4.9-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit 6780db244d6b1537d139dea0ec8aad10cf9e4adb ]
syzbot produced a nice report [1]
Issue here is that a recvmmsg() managed to leak 8 bytes of kernel memory to user space, because sin_zero (padding field) was not properly cleared.
[1] BUG: KMSAN: uninit-value in copy_to_user include/linux/uaccess.h:184 [inline] BUG: KMSAN: uninit-value in move_addr_to_user+0x32e/0x530 net/socket.c:227 CPU: 1 PID: 3586 Comm: syzkaller481044 Not tainted 4.16.0+ #82 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x185/0x1d0 lib/dump_stack.c:53 kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067 kmsan_internal_check_memory+0x164/0x1d0 mm/kmsan/kmsan.c:1176 kmsan_copy_to_user+0x69/0x160 mm/kmsan/kmsan.c:1199 copy_to_user include/linux/uaccess.h:184 [inline] move_addr_to_user+0x32e/0x530 net/socket.c:227 ___sys_recvmsg+0x4e2/0x810 net/socket.c:2211 __sys_recvmmsg+0x54e/0xdb0 net/socket.c:2313 SYSC_recvmmsg+0x29b/0x3e0 net/socket.c:2394 SyS_recvmmsg+0x76/0xa0 net/socket.c:2378 do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x3d/0xa2 RIP: 0033:0x4401c9 RSP: 002b:00007ffc56f73098 EFLAGS: 00000217 ORIG_RAX: 000000000000012b RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004401c9 RDX: 0000000000000001 RSI: 0000000020003ac0 RDI: 0000000000000003 RBP: 00000000006ca018 R08: 0000000020003bc0 R09: 0000000000000010 R10: 0000000000000000 R11: 0000000000000217 R12: 0000000000401af0 R13: 0000000000401b80 R14: 0000000000000000 R15: 0000000000000000
Local variable description: ----addr@___sys_recvmsg Variable was created at: ___sys_recvmsg+0xd5/0x810 net/socket.c:2172 __sys_recvmmsg+0x54e/0xdb0 net/socket.c:2313
Bytes 8-15 of 16 are uninitialized
================================================================== Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 3586 Comm: syzkaller481044 Tainted: G B 4.16.0+ #82 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x185/0x1d0 lib/dump_stack.c:53 panic+0x39d/0x940 kernel/panic.c:183 kmsan_report+0x238/0x240 mm/kmsan/kmsan.c:1083 kmsan_internal_check_memory+0x164/0x1d0 mm/kmsan/kmsan.c:1176 kmsan_copy_to_user+0x69/0x160 mm/kmsan/kmsan.c:1199 copy_to_user include/linux/uaccess.h:184 [inline] move_addr_to_user+0x32e/0x530 net/socket.c:227 ___sys_recvmsg+0x4e2/0x810 net/socket.c:2211 __sys_recvmmsg+0x54e/0xdb0 net/socket.c:2313 SYSC_recvmmsg+0x29b/0x3e0 net/socket.c:2394 SyS_recvmmsg+0x76/0xa0 net/socket.c:2378 do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x3d/0xa2
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Eric Dumazet edumazet@google.com Cc: Vlad Yasevich vyasevich@gmail.com Cc: Neil Horman nhorman@tuxdriver.com Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sctp/ipv6.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/net/sctp/ipv6.c +++ b/net/sctp/ipv6.c @@ -727,8 +727,10 @@ static int sctp_v6_addr_to_user(struct s sctp_v6_map_v4(addr); }
- if (addr->sa.sa_family == AF_INET) + if (addr->sa.sa_family == AF_INET) { + memset(addr->v4.sin_zero, 0, sizeof(addr->v4.sin_zero)); return sizeof(struct sockaddr_in); + } return sizeof(struct sockaddr_in6); }