From 06d4c8a80836d76ffec4f71ddb3de94ee93ab40d Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Mon, 24 Jul 2023 14:34:24 -0700 Subject: [PATCH 1/2] af_unix: Fix fortify_panic() in unix_bind_bsd(). syzkaller found a bug in unix_bind_bsd() [0]. We can reproduce it by bind()ing a socket on a path with length 108. 108 is the size of sun_addr of struct sockaddr_un and is the maximum valid length for the pathname socket. When calling bind(), we use struct sockaddr_storage as the actual buffer size, so terminating sun_addr[108] with null is legitimate as done in unix_mkname_bsd(). However, strlen(sunaddr) for such a case causes fortify_panic() if CONFIG_FORTIFY_SOURCE=y. __fortify_strlen() has no idea about the actual buffer size and see the string as unterminated. Let's use strnlen() to allow sun_addr to be unterminated at 107. [0]: detected buffer overflow in __fortify_strlen kernel BUG at lib/string_helpers.c:1031! Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP Modules linked in: CPU: 0 PID: 255 Comm: syz-executor296 Not tainted 6.5.0-rc1-00330-g60cc1f7d0605 #4 Hardware name: linux,dummy-virt (DT) pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : fortify_panic+0x1c/0x20 lib/string_helpers.c:1030 lr : fortify_panic+0x1c/0x20 lib/string_helpers.c:1030 sp : ffff800089817af0 x29: ffff800089817af0 x28: ffff800089817b40 x27: 1ffff00011302f68 x26: 000000000000006e x25: 0000000000000012 x24: ffff800087e60140 x23: dfff800000000000 x22: ffff800089817c20 x21: ffff800089817c8e x20: 000000000000006c x19: ffff00000c323900 x18: ffff800086ab1630 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000001 x14: 1ffff00011302eb8 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000000 x10: 0000000000000000 x9 : 64a26b65474d2a00 x8 : 64a26b65474d2a00 x7 : 0000000000000001 x6 : 0000000000000001 x5 : ffff800089817438 x4 : ffff800086ac99e0 x3 : ffff800080f19e8c x2 : 0000000000000001 x1 : 0000000100000000 x0 : 000000000000002c Call trace: fortify_panic+0x1c/0x20 lib/string_helpers.c:1030 _Z16__fortify_strlenPKcU25pass_dynamic_object_size1 include/linux/fortify-string.h:217 [inline] unix_bind_bsd net/unix/af_unix.c:1212 [inline] unix_bind+0xba8/0xc58 net/unix/af_unix.c:1326 __sys_bind+0x1ac/0x248 net/socket.c:1792 __do_sys_bind net/socket.c:1803 [inline] __se_sys_bind net/socket.c:1801 [inline] __arm64_sys_bind+0x7c/0x94 net/socket.c:1801 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2c0 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x134/0x240 arch/arm64/kernel/syscall.c:139 do_el0_svc+0x64/0x198 arch/arm64/kernel/syscall.c:188 el0_svc+0x2c/0x7c arch/arm64/kernel/entry-common.c:647 el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:665 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:591 Code: aa0003e1 d0000e80 91030000 97ffc91a (d4210000) Fixes: df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3") Reported-by: syzkaller Suggested-by: Kees Cook Signed-off-by: Kuniyuki Iwashima Link: https://lore.kernel.org/r/20230724213425.22920-2-kuniyu@amazon.com Reviewed-by: Simon Horman Reviewed-by: Kees Cook Signed-off-by: Jakub Kicinski --- net/unix/af_unix.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 123b35ddfd71..bbacf4c60fe3 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1208,10 +1208,8 @@ static int unix_bind_bsd(struct sock *sk, struct sockaddr_un *sunaddr, struct path parent; int err; - unix_mkname_bsd(sunaddr, addr_len); - addr_len = strlen(sunaddr->sun_path) + - offsetof(struct sockaddr_un, sun_path) + 1; - + addr_len = strnlen(sunaddr->sun_path, sizeof(sunaddr->sun_path)) + + offsetof(struct sockaddr_un, sun_path) + 1; addr = unix_create_addr(sunaddr, addr_len); if (!addr) return -ENOMEM; From a0ade8404c3bc2bf2631cb0f20d372eed22d9d96 Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Mon, 24 Jul 2023 14:34:25 -0700 Subject: [PATCH 2/2] af_packet: Fix warning of fortified memcpy() in packet_getname(). syzkaller found a warning in packet_getname() [0], where we try to copy 16 bytes to sockaddr_ll.sll_addr[8]. Some devices (ip6gre, vti6, ip6tnl) have 16 bytes address expressed by struct in6_addr. Also, Infiniband has 32 bytes as MAX_ADDR_LEN. The write seems to overflow, but actually not since we use struct sockaddr_storage defined in __sys_getsockname() and its size is 128 (_K_SS_MAXSIZE) bytes. Thus, we have sufficient room after sll_addr[] as __data[]. To avoid the warning, let's add a flex array member union-ed with sll_addr. Another option would be to use strncpy() and limit the copied length to sizeof(sll_addr), but it will return the partial address and break an application that passes sockaddr_storage to getsockname(). [0]: memcpy: detected field-spanning write (size 16) of single field "sll->sll_addr" at net/packet/af_packet.c:3604 (size 8) WARNING: CPU: 0 PID: 255 at net/packet/af_packet.c:3604 packet_getname+0x25c/0x3a0 net/packet/af_packet.c:3604 Modules linked in: CPU: 0 PID: 255 Comm: syz-executor750 Not tainted 6.5.0-rc1-00330-g60cc1f7d0605 #4 Hardware name: linux,dummy-virt (DT) pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : packet_getname+0x25c/0x3a0 net/packet/af_packet.c:3604 lr : packet_getname+0x25c/0x3a0 net/packet/af_packet.c:3604 sp : ffff800089887bc0 x29: ffff800089887bc0 x28: ffff000010f80f80 x27: 0000000000000003 x26: dfff800000000000 x25: ffff700011310f80 x24: ffff800087d55000 x23: dfff800000000000 x22: ffff800089887c2c x21: 0000000000000010 x20: ffff00000de08310 x19: ffff800089887c20 x18: ffff800086ab1630 x17: 20646c6569662065 x16: 6c676e697320666f x15: 0000000000000001 x14: 1fffe0000d56d7ca x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000000 x10: 0000000000000000 x9 : 3e60944c3da92b00 x8 : 3e60944c3da92b00 x7 : 0000000000000001 x6 : 0000000000000001 x5 : ffff8000898874f8 x4 : ffff800086ac99e0 x3 : ffff8000803f8808 x2 : 0000000000000001 x1 : 0000000100000000 x0 : 0000000000000000 Call trace: packet_getname+0x25c/0x3a0 net/packet/af_packet.c:3604 __sys_getsockname+0x168/0x24c net/socket.c:2042 __do_sys_getsockname net/socket.c:2057 [inline] __se_sys_getsockname net/socket.c:2054 [inline] __arm64_sys_getsockname+0x7c/0x94 net/socket.c:2054 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2c0 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x134/0x240 arch/arm64/kernel/syscall.c:139 do_el0_svc+0x64/0x198 arch/arm64/kernel/syscall.c:188 el0_svc+0x2c/0x7c arch/arm64/kernel/entry-common.c:647 el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:665 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:591 Fixes: df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3") Reported-by: syzkaller Suggested-by: Kees Cook Signed-off-by: Kuniyuki Iwashima Link: https://lore.kernel.org/r/20230724213425.22920-3-kuniyu@amazon.com Reviewed-by: Simon Horman Reviewed-by: Kees Cook Signed-off-by: Jakub Kicinski --- include/uapi/linux/if_packet.h | 6 +++++- net/packet/af_packet.c | 2 +- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/if_packet.h b/include/uapi/linux/if_packet.h index 9efc42382fdb..4d0ad22f83b5 100644 --- a/include/uapi/linux/if_packet.h +++ b/include/uapi/linux/if_packet.h @@ -18,7 +18,11 @@ struct sockaddr_ll { unsigned short sll_hatype; unsigned char sll_pkttype; unsigned char sll_halen; - unsigned char sll_addr[8]; + union { + unsigned char sll_addr[8]; + /* Actual length is in sll_halen. */ + __DECLARE_FLEX_ARRAY(unsigned char, sll_addr_flex); + }; }; /* Packet types */ diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 85ff90a03b0c..8e3ddec4c3d5 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -3601,7 +3601,7 @@ static int packet_getname(struct socket *sock, struct sockaddr *uaddr, if (dev) { sll->sll_hatype = dev->type; sll->sll_halen = dev->addr_len; - memcpy(sll->sll_addr, dev->dev_addr, dev->addr_len); + memcpy(sll->sll_addr_flex, dev->dev_addr, dev->addr_len); } else { sll->sll_hatype = 0; /* Bad: we have no ARPHRD_UNSPEC */ sll->sll_halen = 0;