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arm64: Reject modules with internal alternative callbacks

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During module loading, check if a callback function used by the
alternatives specified in the '.altinstruction' ELF section (if present)
is located in core kernel .text. If not fail module loading before
callback is called.

Reported-by: Fanqin Cui <cuifq1@chinatelecom.cn>
Closes: https://lore.kernel.org/all/20250807072700.348514-1-fanqincui@163.com/
Signed-off-by: Adrian Barnaś <abarnas@google.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
[will: Folded in 'noinstr' tweak from Mark]
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Adrian Barnaś 2025-09-22 13:04:27 +00:00 committed by Will Deacon
parent 6d4a0fbd34
commit 8e8ae78896
3 changed files with 24 additions and 11 deletions
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7
arch/arm64/include/asm/alternative.h
View File

@ -26,9 +26,12 @@ void __init apply_alternatives_all(void);
bool alternative_is_applied(u16 cpucap);
#ifdef CONFIG_MODULES
void apply_alternatives_module(void *start, size_t length);
int apply_alternatives_module(void *start, size_t length);
#else
static inline void apply_alternatives_module(void *start, size_t length) { }
static inline int apply_alternatives_module(void *start, size_t length)
{
return 0;
}
#endif
void alt_cb_patch_nops(struct alt_instr *alt, __le32 *origptr,

19
arch/arm64/kernel/alternative.c
View File

@ -139,9 +139,9 @@ static noinstr void clean_dcache_range_nopatch(u64 start, u64 end)
} while (cur += d_size, cur < end);
}
static void __apply_alternatives(const struct alt_region *region,
bool is_module,
unsigned long *cpucap_mask)
static int __apply_alternatives(const struct alt_region *region,
bool is_module,
unsigned long *cpucap_mask)
{
struct alt_instr *alt;
__le32 *origptr, *updptr;
@ -166,10 +166,13 @@ static void __apply_alternatives(const struct alt_region *region,
updptr = is_module ? origptr : lm_alias(origptr);
nr_inst = alt->orig_len / AARCH64_INSN_SIZE;
if (ALT_HAS_CB(alt))
if (ALT_HAS_CB(alt)) {
alt_cb = ALT_REPL_PTR(alt);
else
if (is_module && !core_kernel_text((unsigned long)alt_cb))
return -ENOEXEC;
} else {
alt_cb = patch_alternative;
}
alt_cb(alt, origptr, updptr, nr_inst);
@ -193,6 +196,8 @@ static void __apply_alternatives(const struct alt_region *region,
bitmap_and(applied_alternatives, applied_alternatives,
system_cpucaps, ARM64_NCAPS);
}
return 0;
}
static void __init apply_alternatives_vdso(void)
@ -277,7 +282,7 @@ void __init apply_boot_alternatives(void)
}
#ifdef CONFIG_MODULES
void apply_alternatives_module(void *start, size_t length)
int apply_alternatives_module(void *start, size_t length)
{
struct alt_region region = {
.begin = start,
@ -287,7 +292,7 @@ void apply_alternatives_module(void *start, size_t length)
bitmap_fill(all_capabilities, ARM64_NCAPS);
__apply_alternatives(&region, true, &all_capabilities[0]);
return __apply_alternatives(&region, true, &all_capabilities[0]);
}
#endif

9
arch/arm64/kernel/module.c
View File

@ -489,8 +489,13 @@ int module_finalize(const Elf_Ehdr *hdr,
int ret;
s = find_section(hdr, sechdrs, ".altinstructions");
if (s)
apply_alternatives_module((void *)s->sh_addr, s->sh_size);
if (s) {
ret = apply_alternatives_module((void *)s->sh_addr, s->sh_size);
if (ret < 0) {
pr_err("module %s: error occurred when applying alternatives\n", me->name);
return ret;
}
}
if (scs_is_dynamic()) {
s = find_section(hdr, sechdrs, ".init.eh_frame");