From 21c7063f6d08ab9afa088584939791bee0c177e5 Mon Sep 17 00:00:00 2001 From: Xu Kuohai Date: Fri, 19 Jul 2024 19:00:51 +0800 Subject: [PATCH 1/8] bpf, lsm: Add disabled BPF LSM hook list Add a disabled hooks list for BPF LSM. progs being attached to the listed hooks will be rejected by the verifier. Suggested-by: KP Singh Signed-off-by: Xu Kuohai Link: https://lore.kernel.org/r/20240719110059.797546-2-xukuohai@huaweicloud.com Signed-off-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko --- kernel/bpf/bpf_lsm.c | 31 +++++++++++++++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c index 08a338e1f231..1f596ad6257c 100644 --- a/kernel/bpf/bpf_lsm.c +++ b/kernel/bpf/bpf_lsm.c @@ -36,6 +36,24 @@ BTF_SET_START(bpf_lsm_hooks) #undef LSM_HOOK BTF_SET_END(bpf_lsm_hooks) +BTF_SET_START(bpf_lsm_disabled_hooks) +BTF_ID(func, bpf_lsm_vm_enough_memory) +BTF_ID(func, bpf_lsm_inode_need_killpriv) +BTF_ID(func, bpf_lsm_inode_getsecurity) +BTF_ID(func, bpf_lsm_inode_listsecurity) +BTF_ID(func, bpf_lsm_inode_copy_up_xattr) +BTF_ID(func, bpf_lsm_getselfattr) +BTF_ID(func, bpf_lsm_getprocattr) +BTF_ID(func, bpf_lsm_setprocattr) +#ifdef CONFIG_KEYS +BTF_ID(func, bpf_lsm_key_getsecurity) +#endif +#ifdef CONFIG_AUDIT +BTF_ID(func, bpf_lsm_audit_rule_match) +#endif +BTF_ID(func, bpf_lsm_ismaclabel) +BTF_SET_END(bpf_lsm_disabled_hooks) + /* List of LSM hooks that should operate on 'current' cgroup regardless * of function signature. */ @@ -97,15 +115,24 @@ void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog, int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog, const struct bpf_prog *prog) { + u32 btf_id = prog->aux->attach_btf_id; + const char *func_name = prog->aux->attach_func_name; + if (!prog->gpl_compatible) { bpf_log(vlog, "LSM programs must have a GPL compatible license\n"); return -EINVAL; } - if (!btf_id_set_contains(&bpf_lsm_hooks, prog->aux->attach_btf_id)) { + if (btf_id_set_contains(&bpf_lsm_disabled_hooks, btf_id)) { + bpf_log(vlog, "attach_btf_id %u points to disabled hook %s\n", + btf_id, func_name); + return -EINVAL; + } + + if (!btf_id_set_contains(&bpf_lsm_hooks, btf_id)) { bpf_log(vlog, "attach_btf_id %u points to wrong type name %s\n", - prog->aux->attach_btf_id, prog->aux->attach_func_name); + btf_id, func_name); return -EINVAL; } From 5d99e198be279045e6ecefe220f5c52f8ce9bfd5 Mon Sep 17 00:00:00 2001 From: Xu Kuohai Date: Fri, 19 Jul 2024 19:00:52 +0800 Subject: [PATCH 2/8] bpf, lsm: Add check for BPF LSM return value A bpf prog returning a positive number attached to file_alloc_security hook makes kernel panic. This happens because file system can not filter out the positive number returned by the LSM prog using IS_ERR, and misinterprets this positive number as a file pointer. Given that hook file_alloc_security never returned positive number before the introduction of BPF LSM, and other BPF LSM hooks may encounter similar issues, this patch adds LSM return value check in verifier, to ensure no unexpected value is returned. Fixes: 520b7aa00d8c ("bpf: lsm: Initialize the BPF LSM hooks") Reported-by: Xin Liu Signed-off-by: Xu Kuohai Acked-by: Eduard Zingerman Link: https://lore.kernel.org/r/20240719110059.797546-3-xukuohai@huaweicloud.com Signed-off-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko --- include/linux/bpf.h | 1 + include/linux/bpf_lsm.h | 8 ++++++ kernel/bpf/bpf_lsm.c | 34 ++++++++++++++++++++++- kernel/bpf/btf.c | 5 +++- kernel/bpf/verifier.c | 60 ++++++++++++++++++++++++++++++++++------- 5 files changed, 97 insertions(+), 11 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 4c54864316ee..5739cc9986f8 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -927,6 +927,7 @@ struct bpf_insn_access_aux { }; }; struct bpf_verifier_log *log; /* for verbose logs */ + bool is_retval; /* is accessing function return value ? */ }; static inline void diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h index 1de7ece5d36d..aefcd6564251 100644 --- a/include/linux/bpf_lsm.h +++ b/include/linux/bpf_lsm.h @@ -9,6 +9,7 @@ #include #include +#include #include #ifdef CONFIG_BPF_LSM @@ -45,6 +46,8 @@ void bpf_inode_storage_free(struct inode *inode); void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog, bpf_func_t *bpf_func); +int bpf_lsm_get_retval_range(const struct bpf_prog *prog, + struct bpf_retval_range *range); #else /* !CONFIG_BPF_LSM */ static inline bool bpf_lsm_is_sleepable_hook(u32 btf_id) @@ -78,6 +81,11 @@ static inline void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog, { } +static inline int bpf_lsm_get_retval_range(const struct bpf_prog *prog, + struct bpf_retval_range *range) +{ + return -EOPNOTSUPP; +} #endif /* CONFIG_BPF_LSM */ #endif /* _LINUX_BPF_LSM_H */ diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c index 1f596ad6257c..6292ac5f9bd1 100644 --- a/kernel/bpf/bpf_lsm.c +++ b/kernel/bpf/bpf_lsm.c @@ -11,7 +11,6 @@ #include #include #include -#include #include #include #include @@ -417,3 +416,36 @@ const struct bpf_verifier_ops lsm_verifier_ops = { .get_func_proto = bpf_lsm_func_proto, .is_valid_access = btf_ctx_access, }; + +/* hooks return 0 or 1 */ +BTF_SET_START(bool_lsm_hooks) +#ifdef CONFIG_SECURITY_NETWORK_XFRM +BTF_ID(func, bpf_lsm_xfrm_state_pol_flow_match) +#endif +#ifdef CONFIG_AUDIT +BTF_ID(func, bpf_lsm_audit_rule_known) +#endif +BTF_ID(func, bpf_lsm_inode_xattr_skipcap) +BTF_SET_END(bool_lsm_hooks) + +int bpf_lsm_get_retval_range(const struct bpf_prog *prog, + struct bpf_retval_range *retval_range) +{ + /* no return value range for void hooks */ + if (!prog->aux->attach_func_proto->type) + return -EINVAL; + + if (btf_id_set_contains(&bool_lsm_hooks, prog->aux->attach_btf_id)) { + retval_range->minval = 0; + retval_range->maxval = 1; + } else { + /* All other available LSM hooks, except task_prctl, return 0 + * on success and negative error code on failure. + * To keep things simple, we only allow bpf progs to return 0 + * or negative errno for task_prctl too. + */ + retval_range->minval = -MAX_ERRNO; + retval_range->maxval = 0; + } + return 0; +} diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 520f49f422fe..95426d5b634e 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6416,8 +6416,11 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, if (arg == nr_args) { switch (prog->expected_attach_type) { - case BPF_LSM_CGROUP: case BPF_LSM_MAC: + /* mark we are accessing the return value */ + info->is_retval = true; + fallthrough; + case BPF_LSM_CGROUP: case BPF_TRACE_FEXIT: /* When LSM programs are attached to void LSM hooks * they use FEXIT trampolines and when attached to diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 247a038d3a14..8caa7322f031 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2334,6 +2334,25 @@ static void mark_reg_unknown(struct bpf_verifier_env *env, __mark_reg_unknown(env, regs + regno); } +static int __mark_reg_s32_range(struct bpf_verifier_env *env, + struct bpf_reg_state *regs, + u32 regno, + s32 s32_min, + s32 s32_max) +{ + struct bpf_reg_state *reg = regs + regno; + + reg->s32_min_value = max_t(s32, reg->s32_min_value, s32_min); + reg->s32_max_value = min_t(s32, reg->s32_max_value, s32_max); + + reg->smin_value = max_t(s64, reg->smin_value, s32_min); + reg->smax_value = min_t(s64, reg->smax_value, s32_max); + + reg_bounds_sync(reg); + + return reg_bounds_sanity_check(env, reg, "s32_range"); +} + static void __mark_reg_not_init(const struct bpf_verifier_env *env, struct bpf_reg_state *reg) { @@ -5607,11 +5626,12 @@ static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off, /* check access to 'struct bpf_context' fields. Supports fixed offsets only */ static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off, int size, enum bpf_access_type t, enum bpf_reg_type *reg_type, - struct btf **btf, u32 *btf_id) + struct btf **btf, u32 *btf_id, bool *is_retval) { struct bpf_insn_access_aux info = { .reg_type = *reg_type, .log = &env->log, + .is_retval = false, }; if (env->ops->is_valid_access && @@ -5624,6 +5644,7 @@ static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off, * type of narrower access. */ *reg_type = info.reg_type; + *is_retval = info.is_retval; if (base_type(*reg_type) == PTR_TO_BTF_ID) { *btf = info.btf; @@ -6792,6 +6813,17 @@ static int check_stack_access_within_bounds( return grow_stack_state(env, state, -min_off /* size */); } +static bool get_func_retval_range(struct bpf_prog *prog, + struct bpf_retval_range *range) +{ + if (prog->type == BPF_PROG_TYPE_LSM && + prog->expected_attach_type == BPF_LSM_MAC && + !bpf_lsm_get_retval_range(prog, range)) { + return true; + } + return false; +} + /* check whether memory at (regno + off) is accessible for t = (read | write) * if t==write, value_regno is a register which value is stored into memory * if t==read, value_regno is a register which will receive the value from memory @@ -6896,6 +6928,8 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn if (!err && value_regno >= 0 && (t == BPF_READ || rdonly_mem)) mark_reg_unknown(env, regs, value_regno); } else if (reg->type == PTR_TO_CTX) { + bool is_retval = false; + struct bpf_retval_range range; enum bpf_reg_type reg_type = SCALAR_VALUE; struct btf *btf = NULL; u32 btf_id = 0; @@ -6911,7 +6945,7 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn return err; err = check_ctx_access(env, insn_idx, off, size, t, ®_type, &btf, - &btf_id); + &btf_id, &is_retval); if (err) verbose_linfo(env, insn_idx, "; "); if (!err && t == BPF_READ && value_regno >= 0) { @@ -6920,7 +6954,14 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn * case, we know the offset is zero. */ if (reg_type == SCALAR_VALUE) { - mark_reg_unknown(env, regs, value_regno); + if (is_retval && get_func_retval_range(env->prog, &range)) { + err = __mark_reg_s32_range(env, regs, value_regno, + range.minval, range.maxval); + if (err) + return err; + } else { + mark_reg_unknown(env, regs, value_regno); + } } else { mark_reg_known_zero(env, regs, value_regno); @@ -15762,12 +15803,13 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char case BPF_PROG_TYPE_LSM: if (env->prog->expected_attach_type != BPF_LSM_CGROUP) { - /* Regular BPF_PROG_TYPE_LSM programs can return - * any value. - */ - return 0; - } - if (!env->prog->aux->attach_func_proto->type) { + /* no range found, any return value is allowed */ + if (!get_func_retval_range(env->prog, &range)) + return 0; + /* no restricted range, any return value is allowed */ + if (range.minval == S32_MIN && range.maxval == S32_MAX) + return 0; + } else if (!env->prog->aux->attach_func_proto->type) { /* Make sure programs that attach to void * hooks don't try to modify return value. */ From 28ead3eaabc16ecc907cfb71876da028080f6356 Mon Sep 17 00:00:00 2001 From: Xu Kuohai Date: Fri, 19 Jul 2024 19:00:53 +0800 Subject: [PATCH 3/8] bpf: Prevent tail call between progs attached to different hooks bpf progs can be attached to kernel functions, and the attached functions can take different parameters or return different return values. If prog attached to one kernel function tail calls prog attached to another kernel function, the ctx access or return value verification could be bypassed. For example, if prog1 is attached to func1 which takes only 1 parameter and prog2 is attached to func2 which takes two parameters. Since verifier assumes the bpf ctx passed to prog2 is constructed based on func2's prototype, verifier allows prog2 to access the second parameter from the bpf ctx passed to it. The problem is that verifier does not prevent prog1 from passing its bpf ctx to prog2 via tail call. In this case, the bpf ctx passed to prog2 is constructed from func1 instead of func2, that is, the assumption for ctx access verification is bypassed. Another example, if BPF LSM prog1 is attached to hook file_alloc_security, and BPF LSM prog2 is attached to hook bpf_lsm_audit_rule_known. Verifier knows the return value rules for these two hooks, e.g. it is legal for bpf_lsm_audit_rule_known to return positive number 1, and it is illegal for file_alloc_security to return positive number. So verifier allows prog2 to return positive number 1, but does not allow prog1 to return positive number. The problem is that verifier does not prevent prog1 from calling prog2 via tail call. In this case, prog2's return value 1 will be used as the return value for prog1's hook file_alloc_security. That is, the return value rule is bypassed. This patch adds restriction for tail call to prevent such bypasses. Signed-off-by: Xu Kuohai Link: https://lore.kernel.org/r/20240719110059.797546-4-xukuohai@huaweicloud.com Signed-off-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko --- include/linux/bpf.h | 1 + kernel/bpf/core.c | 21 ++++++++++++++++++--- 2 files changed, 19 insertions(+), 3 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 5739cc9986f8..f16d0753f518 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -294,6 +294,7 @@ struct bpf_map { * same prog type, JITed flag and xdp_has_frags flag. */ struct { + const struct btf_type *attach_func_proto; spinlock_t lock; enum bpf_prog_type type; bool jited; diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 7ee62e38faf0..4e07cc057d6f 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -2302,6 +2302,7 @@ bool bpf_prog_map_compatible(struct bpf_map *map, { enum bpf_prog_type prog_type = resolve_prog_type(fp); bool ret; + struct bpf_prog_aux *aux = fp->aux; if (fp->kprobe_override) return false; @@ -2311,7 +2312,7 @@ bool bpf_prog_map_compatible(struct bpf_map *map, * in the case of devmap and cpumap). Until device checks * are implemented, prohibit adding dev-bound programs to program maps. */ - if (bpf_prog_is_dev_bound(fp->aux)) + if (bpf_prog_is_dev_bound(aux)) return false; spin_lock(&map->owner.lock); @@ -2321,12 +2322,26 @@ bool bpf_prog_map_compatible(struct bpf_map *map, */ map->owner.type = prog_type; map->owner.jited = fp->jited; - map->owner.xdp_has_frags = fp->aux->xdp_has_frags; + map->owner.xdp_has_frags = aux->xdp_has_frags; + map->owner.attach_func_proto = aux->attach_func_proto; ret = true; } else { ret = map->owner.type == prog_type && map->owner.jited == fp->jited && - map->owner.xdp_has_frags == fp->aux->xdp_has_frags; + map->owner.xdp_has_frags == aux->xdp_has_frags; + if (ret && + map->owner.attach_func_proto != aux->attach_func_proto) { + switch (prog_type) { + case BPF_PROG_TYPE_TRACING: + case BPF_PROG_TYPE_LSM: + case BPF_PROG_TYPE_EXT: + case BPF_PROG_TYPE_STRUCT_OPS: + ret = false; + break; + default: + break; + } + } } spin_unlock(&map->owner.lock); From 763aa759d3b2c4f95b11855e3d37b860860107e2 Mon Sep 17 00:00:00 2001 From: Xu Kuohai Date: Fri, 19 Jul 2024 19:00:54 +0800 Subject: [PATCH 4/8] bpf: Fix compare error in function retval_range_within After checking lsm hook return range in verifier, the test case "test_progs -t test_lsm" failed, and the failure log says: libbpf: prog 'test_int_hook': BPF program load failed: Invalid argument libbpf: prog 'test_int_hook': -- BEGIN PROG LOAD LOG -- 0: R1=ctx() R10=fp0 ; int BPF_PROG(test_int_hook, struct vm_area_struct *vma, @ lsm.c:89 0: (79) r0 = *(u64 *)(r1 +24) ; R0_w=scalar(smin=smin32=-4095,smax=smax32=0) R1=ctx() [...] 24: (b4) w0 = -1 ; R0_w=0xffffffff ; int BPF_PROG(test_int_hook, struct vm_area_struct *vma, @ lsm.c:89 25: (95) exit At program exit the register R0 has smin=4294967295 smax=4294967295 should have been in [-4095, 0] It can be seen that instruction "w0 = -1" zero extended -1 to 64-bit register r0, setting both smin and smax values of r0 to 4294967295. This resulted in a false reject when r0 was checked with range [-4095, 0]. Given bpf lsm does not return 64-bit values, this patch fixes it by changing the compare between r0 and return range from 64-bit operation to 32-bit operation for bpf lsm. Fixes: 8fa4ecd49b81 ("bpf: enforce exact retval range on subprog/callback exit") Signed-off-by: Xu Kuohai Acked-by: Shung-Hsi Yu Link: https://lore.kernel.org/r/20240719110059.797546-5-xukuohai@huaweicloud.com Signed-off-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko --- kernel/bpf/verifier.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 8caa7322f031..c419005a29dc 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -9984,9 +9984,13 @@ static bool in_rbtree_lock_required_cb(struct bpf_verifier_env *env) return is_rbtree_lock_required_kfunc(kfunc_btf_id); } -static bool retval_range_within(struct bpf_retval_range range, const struct bpf_reg_state *reg) +static bool retval_range_within(struct bpf_retval_range range, const struct bpf_reg_state *reg, + bool return_32bit) { - return range.minval <= reg->smin_value && reg->smax_value <= range.maxval; + if (return_32bit) + return range.minval <= reg->s32_min_value && reg->s32_max_value <= range.maxval; + else + return range.minval <= reg->smin_value && reg->smax_value <= range.maxval; } static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) @@ -10023,8 +10027,8 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) if (err) return err; - /* enforce R0 return value range */ - if (!retval_range_within(callee->callback_ret_range, r0)) { + /* enforce R0 return value range, and bpf_callback_t returns 64bit */ + if (!retval_range_within(callee->callback_ret_range, r0, false)) { verbose_invalid_scalar(env, r0, callee->callback_ret_range, "At callback return", "R0"); return -EINVAL; @@ -15698,6 +15702,7 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char int err; struct bpf_func_state *frame = env->cur_state->frame[0]; const bool is_subprog = frame->subprogno; + bool return_32bit = false; /* LSM and struct_ops func-ptr's return type could be "void" */ if (!is_subprog || frame->in_exception_callback_fn) { @@ -15809,6 +15814,7 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char /* no restricted range, any return value is allowed */ if (range.minval == S32_MIN && range.maxval == S32_MAX) return 0; + return_32bit = true; } else if (!env->prog->aux->attach_func_proto->type) { /* Make sure programs that attach to void * hooks don't try to modify return value. @@ -15839,7 +15845,7 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char if (err) return err; - if (!retval_range_within(range, reg)) { + if (!retval_range_within(range, reg, return_32bit)) { verbose_invalid_scalar(env, reg, range, exit_ctx, reg_name); if (!is_subprog && prog->expected_attach_type == BPF_LSM_CGROUP && From 4dc7556490d77d5046844e7731d5d0a3055a3448 Mon Sep 17 00:00:00 2001 From: Xu Kuohai Date: Fri, 19 Jul 2024 19:00:56 +0800 Subject: [PATCH 5/8] selftests/bpf: Avoid load failure for token_lsm.c The compiler optimized the two bpf progs in token_lsm.c to make return value from the bool variable in the "return -1" path, causing an unexpected rejection: 0: R1=ctx() R10=fp0 ; int BPF_PROG(bpf_token_capable, struct bpf_token *token, int cap) @ bpf_lsm.c:17 0: (b7) r6 = 0 ; R6_w=0 ; if (my_pid == 0 || my_pid != (bpf_get_current_pid_tgid() >> 32)) @ bpf_lsm.c:19 1: (18) r1 = 0xffffc9000102a000 ; R1_w=map_value(map=bpf_lsm.bss,ks=4,vs=5) 3: (61) r7 = *(u32 *)(r1 +0) ; R1_w=map_value(map=bpf_lsm.bss,ks=4,vs=5) R7_w=scalar(smin=0,smax=umax=0xffffffff,var_off=(0x0; 0xffffffff)) 4: (15) if r7 == 0x0 goto pc+11 ; R7_w=scalar(smin=umin=umin32=1,smax=umax=0xffffffff,var_off=(0x0; 0xffffffff)) 5: (67) r7 <<= 32 ; R7_w=scalar(smax=0x7fffffff00000000,umax=0xffffffff00000000,smin32=0,smax32=umax32=0,var_off=(0x0; 0xffffffff00000000)) 6: (c7) r7 s>>= 32 ; R7_w=scalar(smin=0xffffffff80000000,smax=0x7fffffff) 7: (85) call bpf_get_current_pid_tgid#14 ; R0=scalar() 8: (77) r0 >>= 32 ; R0_w=scalar(smin=0,smax=umax=0xffffffff,var_off=(0x0; 0xffffffff)) 9: (5d) if r0 != r7 goto pc+6 ; R0_w=scalar(smin=smin32=0,smax=umax=umax32=0x7fffffff,var_off=(0x0; 0x7fffffff)) R7=scalar(smin=smin32=0,smax=umax=umax32=0x7fffffff,var_off=(0x0; 0x7fffffff)) ; if (reject_capable) @ bpf_lsm.c:21 10: (18) r1 = 0xffffc9000102a004 ; R1_w=map_value(map=bpf_lsm.bss,ks=4,vs=5,off=4) 12: (71) r6 = *(u8 *)(r1 +0) ; R1_w=map_value(map=bpf_lsm.bss,ks=4,vs=5,off=4) R6_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=255,var_off=(0x0; 0xff)) ; @ bpf_lsm.c:0 13: (87) r6 = -r6 ; R6_w=scalar() 14: (67) r6 <<= 56 ; R6_w=scalar(smax=0x7f00000000000000,umax=0xff00000000000000,smin32=0,smax32=umax32=0,var_off=(0x0; 0xff00000000000000)) 15: (c7) r6 s>>= 56 ; R6_w=scalar(smin=smin32=-128,smax=smax32=127) ; int BPF_PROG(bpf_token_capable, struct bpf_token *token, int cap) @ bpf_lsm.c:17 16: (bf) r0 = r6 ; R0_w=scalar(id=1,smin=smin32=-128,smax=smax32=127) R6_w=scalar(id=1,smin=smin32=-128,smax=smax32=127) 17: (95) exit At program exit the register R0 has smin=-128 smax=127 should have been in [-4095, 0] To avoid this failure, change the variable type from bool to int. Signed-off-by: Xu Kuohai Link: https://lore.kernel.org/r/20240719110059.797546-7-xukuohai@huaweicloud.com Signed-off-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko --- tools/testing/selftests/bpf/progs/token_lsm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/bpf/progs/token_lsm.c b/tools/testing/selftests/bpf/progs/token_lsm.c index e4d59b6ba743..a6002d073b1b 100644 --- a/tools/testing/selftests/bpf/progs/token_lsm.c +++ b/tools/testing/selftests/bpf/progs/token_lsm.c @@ -8,8 +8,8 @@ char _license[] SEC("license") = "GPL"; int my_pid; -bool reject_capable; -bool reject_cmd; +int reject_capable; +int reject_cmd; SEC("lsm/bpf_token_capable") int BPF_PROG(token_capable, struct bpf_token *token, int cap) From 2b23b6c0f03c94dbacff2abdfd45490eca9d7f6e Mon Sep 17 00:00:00 2001 From: Xu Kuohai Date: Fri, 19 Jul 2024 19:00:57 +0800 Subject: [PATCH 6/8] selftests/bpf: Add return value checks for failed tests The return ranges of some bpf lsm test progs can not be deduced by the verifier accurately. To avoid erroneous rejections, add explicit return value checks for these progs. Signed-off-by: Xu Kuohai Link: https://lore.kernel.org/r/20240719110059.797546-8-xukuohai@huaweicloud.com Signed-off-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko --- tools/testing/selftests/bpf/progs/err.h | 10 ++++++++++ tools/testing/selftests/bpf/progs/test_sig_in_xattr.c | 4 ++++ .../selftests/bpf/progs/test_verify_pkcs7_sig.c | 8 ++++++-- .../selftests/bpf/progs/verifier_global_subprogs.c | 7 ++++++- 4 files changed, 26 insertions(+), 3 deletions(-) diff --git a/tools/testing/selftests/bpf/progs/err.h b/tools/testing/selftests/bpf/progs/err.h index d66d283d9e59..38529779a236 100644 --- a/tools/testing/selftests/bpf/progs/err.h +++ b/tools/testing/selftests/bpf/progs/err.h @@ -5,6 +5,16 @@ #define MAX_ERRNO 4095 #define IS_ERR_VALUE(x) (unsigned long)(void *)(x) >= (unsigned long)-MAX_ERRNO +#define __STR(x) #x + +#define set_if_not_errno_or_zero(x, y) \ +({ \ + asm volatile ("if %0 s< -4095 goto +1\n" \ + "if %0 s<= 0 goto +1\n" \ + "%0 = " __STR(y) "\n" \ + : "+r"(x)); \ +}) + static inline int IS_ERR_OR_NULL(const void *ptr) { return !ptr || IS_ERR_VALUE((unsigned long)ptr); diff --git a/tools/testing/selftests/bpf/progs/test_sig_in_xattr.c b/tools/testing/selftests/bpf/progs/test_sig_in_xattr.c index 2f0eb1334d65..8ef6b39335b6 100644 --- a/tools/testing/selftests/bpf/progs/test_sig_in_xattr.c +++ b/tools/testing/selftests/bpf/progs/test_sig_in_xattr.c @@ -6,6 +6,7 @@ #include #include #include "bpf_kfuncs.h" +#include "err.h" char _license[] SEC("license") = "GPL"; @@ -79,5 +80,8 @@ int BPF_PROG(test_file_open, struct file *f) ret = bpf_verify_pkcs7_signature(&digest_ptr, &sig_ptr, trusted_keyring); bpf_key_put(trusted_keyring); + + set_if_not_errno_or_zero(ret, -EFAULT); + return ret; } diff --git a/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c b/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c index f42e9f3831a1..12034a73ee2d 100644 --- a/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c +++ b/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c @@ -11,6 +11,7 @@ #include #include #include "bpf_kfuncs.h" +#include "err.h" #define MAX_DATA_SIZE (1024 * 1024) #define MAX_SIG_SIZE 1024 @@ -55,12 +56,12 @@ int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size) ret = bpf_probe_read_kernel(&value, sizeof(value), &attr->value); if (ret) - return ret; + goto out; ret = bpf_copy_from_user(data_val, sizeof(struct data), (void *)(unsigned long)value); if (ret) - return ret; + goto out; if (data_val->data_len > sizeof(data_val->data)) return -EINVAL; @@ -84,5 +85,8 @@ int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size) bpf_key_put(trusted_keyring); +out: + set_if_not_errno_or_zero(ret, -EFAULT); + return ret; } diff --git a/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c b/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c index a9fc30ed4d73..20904cd2baa2 100644 --- a/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c +++ b/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c @@ -7,6 +7,7 @@ #include "bpf_misc.h" #include "xdp_metadata.h" #include "bpf_kfuncs.h" +#include "err.h" /* The compiler may be able to detect the access to uninitialized memory in the routines performing out of bound memory accesses and @@ -331,7 +332,11 @@ SEC("?lsm/bpf") __success __log_level(2) int BPF_PROG(arg_tag_ctx_lsm) { - return tracing_subprog_void(ctx) + tracing_subprog_u64(ctx); + int ret; + + ret = tracing_subprog_void(ctx) + tracing_subprog_u64(ctx); + set_if_not_errno_or_zero(ret, -1); + return ret; } SEC("?struct_ops/test_1") From d463dd9c9aa24b17ccb8ed76bdd7768baf857b48 Mon Sep 17 00:00:00 2001 From: Xu Kuohai Date: Fri, 19 Jul 2024 19:00:58 +0800 Subject: [PATCH 7/8] selftests/bpf: Add test for lsm tail call Add test for lsm tail call to ensure tail call can only be used between bpf lsm progs attached to the same hook. Signed-off-by: Xu Kuohai Link: https://lore.kernel.org/r/20240719110059.797546-9-xukuohai@huaweicloud.com Signed-off-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko --- .../selftests/bpf/prog_tests/test_lsm.c | 46 ++++++++++++++++++- .../selftests/bpf/progs/lsm_tailcall.c | 34 ++++++++++++++ 2 files changed, 79 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/bpf/progs/lsm_tailcall.c diff --git a/tools/testing/selftests/bpf/prog_tests/test_lsm.c b/tools/testing/selftests/bpf/prog_tests/test_lsm.c index 16175d579bc7..2a27f3714f5c 100644 --- a/tools/testing/selftests/bpf/prog_tests/test_lsm.c +++ b/tools/testing/selftests/bpf/prog_tests/test_lsm.c @@ -12,6 +12,7 @@ #include #include "lsm.skel.h" +#include "lsm_tailcall.skel.h" char *CMD_ARGS[] = {"true", NULL}; @@ -95,7 +96,7 @@ static int test_lsm(struct lsm *skel) return 0; } -void test_test_lsm(void) +static void test_lsm_basic(void) { struct lsm *skel = NULL; int err; @@ -114,3 +115,46 @@ void test_test_lsm(void) close_prog: lsm__destroy(skel); } + +static void test_lsm_tailcall(void) +{ + struct lsm_tailcall *skel = NULL; + int map_fd, prog_fd; + int err, key; + + skel = lsm_tailcall__open_and_load(); + if (!ASSERT_OK_PTR(skel, "lsm_tailcall__skel_load")) + goto close_prog; + + map_fd = bpf_map__fd(skel->maps.jmp_table); + if (CHECK_FAIL(map_fd < 0)) + goto close_prog; + + prog_fd = bpf_program__fd(skel->progs.lsm_file_permission_prog); + if (CHECK_FAIL(prog_fd < 0)) + goto close_prog; + + key = 0; + err = bpf_map_update_elem(map_fd, &key, &prog_fd, BPF_ANY); + if (CHECK_FAIL(!err)) + goto close_prog; + + prog_fd = bpf_program__fd(skel->progs.lsm_file_alloc_security_prog); + if (CHECK_FAIL(prog_fd < 0)) + goto close_prog; + + err = bpf_map_update_elem(map_fd, &key, &prog_fd, BPF_ANY); + if (CHECK_FAIL(err)) + goto close_prog; + +close_prog: + lsm_tailcall__destroy(skel); +} + +void test_test_lsm(void) +{ + if (test__start_subtest("lsm_basic")) + test_lsm_basic(); + if (test__start_subtest("lsm_tailcall")) + test_lsm_tailcall(); +} diff --git a/tools/testing/selftests/bpf/progs/lsm_tailcall.c b/tools/testing/selftests/bpf/progs/lsm_tailcall.c new file mode 100644 index 000000000000..49c075ce2d4c --- /dev/null +++ b/tools/testing/selftests/bpf/progs/lsm_tailcall.c @@ -0,0 +1,34 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2024 Huawei Technologies Co., Ltd */ + +#include "vmlinux.h" +#include +#include + +char _license[] SEC("license") = "GPL"; + +struct { + __uint(type, BPF_MAP_TYPE_PROG_ARRAY); + __uint(max_entries, 1); + __uint(key_size, sizeof(__u32)); + __uint(value_size, sizeof(__u32)); +} jmp_table SEC(".maps"); + +SEC("lsm/file_permission") +int lsm_file_permission_prog(void *ctx) +{ + return 0; +} + +SEC("lsm/file_alloc_security") +int lsm_file_alloc_security_prog(void *ctx) +{ + return 0; +} + +SEC("lsm/file_alloc_security") +int lsm_file_alloc_security_entry(void *ctx) +{ + bpf_tail_call_static(ctx, &jmp_table, 0); + return 0; +} From 04d8243b1f83251bd599fdd3ea91e89039b6a557 Mon Sep 17 00:00:00 2001 From: Xu Kuohai Date: Fri, 19 Jul 2024 19:00:59 +0800 Subject: [PATCH 8/8] selftests/bpf: Add verifier tests for bpf lsm Add verifier tests to check bpf lsm return values and disabled hooks. Signed-off-by: Xu Kuohai Link: https://lore.kernel.org/r/20240719110059.797546-10-xukuohai@huaweicloud.com Signed-off-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko --- .../selftests/bpf/prog_tests/verifier.c | 2 + .../selftests/bpf/progs/verifier_lsm.c | 162 ++++++++++++++++++ 2 files changed, 164 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/verifier_lsm.c diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c index 9dc3687bc406..ff1c7da1d06e 100644 --- a/tools/testing/selftests/bpf/prog_tests/verifier.c +++ b/tools/testing/selftests/bpf/prog_tests/verifier.c @@ -88,6 +88,7 @@ #include "verifier_xdp.skel.h" #include "verifier_xdp_direct_packet_access.skel.h" #include "verifier_bits_iter.skel.h" +#include "verifier_lsm.skel.h" #define MAX_ENTRIES 11 @@ -206,6 +207,7 @@ void test_verifier_xadd(void) { RUN(verifier_xadd); } void test_verifier_xdp(void) { RUN(verifier_xdp); } void test_verifier_xdp_direct_packet_access(void) { RUN(verifier_xdp_direct_packet_access); } void test_verifier_bits_iter(void) { RUN(verifier_bits_iter); } +void test_verifier_lsm(void) { RUN(verifier_lsm); } static int init_test_val_map(struct bpf_object *obj, char *map_name) { diff --git a/tools/testing/selftests/bpf/progs/verifier_lsm.c b/tools/testing/selftests/bpf/progs/verifier_lsm.c new file mode 100644 index 000000000000..32e5e779cb96 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/verifier_lsm.c @@ -0,0 +1,162 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include "bpf_misc.h" + +SEC("lsm/file_alloc_security") +__description("lsm bpf prog with -4095~0 retval. test 1") +__success +__naked int errno_zero_retval_test1(void *ctx) +{ + asm volatile ( + "r0 = 0;" + "exit;" + ::: __clobber_all); +} + +SEC("lsm/file_alloc_security") +__description("lsm bpf prog with -4095~0 retval. test 2") +__success +__naked int errno_zero_retval_test2(void *ctx) +{ + asm volatile ( + "r0 = -4095;" + "exit;" + ::: __clobber_all); +} + +SEC("lsm/file_mprotect") +__description("lsm bpf prog with -4095~0 retval. test 4") +__failure __msg("R0 has smin=-4096 smax=-4096 should have been in [-4095, 0]") +__naked int errno_zero_retval_test4(void *ctx) +{ + asm volatile ( + "r0 = -4096;" + "exit;" + ::: __clobber_all); +} + +SEC("lsm/file_mprotect") +__description("lsm bpf prog with -4095~0 retval. test 5") +__failure __msg("R0 has smin=4096 smax=4096 should have been in [-4095, 0]") +__naked int errno_zero_retval_test5(void *ctx) +{ + asm volatile ( + "r0 = 4096;" + "exit;" + ::: __clobber_all); +} + +SEC("lsm/file_mprotect") +__description("lsm bpf prog with -4095~0 retval. test 6") +__failure __msg("R0 has smin=1 smax=1 should have been in [-4095, 0]") +__naked int errno_zero_retval_test6(void *ctx) +{ + asm volatile ( + "r0 = 1;" + "exit;" + ::: __clobber_all); +} + +SEC("lsm/audit_rule_known") +__description("lsm bpf prog with bool retval. test 1") +__success +__naked int bool_retval_test1(void *ctx) +{ + asm volatile ( + "r0 = 1;" + "exit;" + ::: __clobber_all); +} + +SEC("lsm/audit_rule_known") +__description("lsm bpf prog with bool retval. test 2") +__success +__success +__naked int bool_retval_test2(void *ctx) +{ + asm volatile ( + "r0 = 0;" + "exit;" + ::: __clobber_all); +} + +SEC("lsm/audit_rule_known") +__description("lsm bpf prog with bool retval. test 3") +__failure __msg("R0 has smin=-1 smax=-1 should have been in [0, 1]") +__naked int bool_retval_test3(void *ctx) +{ + asm volatile ( + "r0 = -1;" + "exit;" + ::: __clobber_all); +} + +SEC("lsm/audit_rule_known") +__description("lsm bpf prog with bool retval. test 4") +__failure __msg("R0 has smin=2 smax=2 should have been in [0, 1]") +__naked int bool_retval_test4(void *ctx) +{ + asm volatile ( + "r0 = 2;" + "exit;" + ::: __clobber_all); +} + +SEC("lsm/file_free_security") +__success +__description("lsm bpf prog with void retval. test 1") +__naked int void_retval_test1(void *ctx) +{ + asm volatile ( + "r0 = -4096;" + "exit;" + ::: __clobber_all); +} + +SEC("lsm/file_free_security") +__success +__description("lsm bpf prog with void retval. test 2") +__naked int void_retval_test2(void *ctx) +{ + asm volatile ( + "r0 = 4096;" + "exit;" + ::: __clobber_all); +} + +SEC("lsm/getprocattr") +__description("lsm disabled hook: getprocattr") +__failure __msg("points to disabled hook") +__naked int disabled_hook_test1(void *ctx) +{ + asm volatile ( + "r0 = 0;" + "exit;" + ::: __clobber_all); +} + +SEC("lsm/setprocattr") +__description("lsm disabled hook: setprocattr") +__failure __msg("points to disabled hook") +__naked int disabled_hook_test2(void *ctx) +{ + asm volatile ( + "r0 = 0;" + "exit;" + ::: __clobber_all); +} + +SEC("lsm/ismaclabel") +__description("lsm disabled hook: ismaclabel") +__failure __msg("points to disabled hook") +__naked int disabled_hook_test3(void *ctx) +{ + asm volatile ( + "r0 = 0;" + "exit;" + ::: __clobber_all); +} + +char _license[] SEC("license") = "GPL";