From: Alexander Potapenko glider@google.com
[ Upstream commit e2f586bd83177d22072b275edd4b8b872daba924 ]
KMSAN (KernelMemorySanitizer, a new error detection tool) reports use of uninitialized memory in selinux_socket_bind():
================================================================== BUG: KMSAN: use of unitialized memory inter: 0 CPU: 3 PID: 1074 Comm: packet2 Tainted: G B 4.8.0-rc6+ #1916 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 0000000000000000 ffff8800882ffb08 ffffffff825759c8 ffff8800882ffa48 ffffffff818bf551 ffffffff85bab870 0000000000000092 ffffffff85bab550 0000000000000000 0000000000000092 00000000bb0009bb 0000000000000002 Call Trace: [< inline >] __dump_stack lib/dump_stack.c:15 [<ffffffff825759c8>] dump_stack+0x238/0x290 lib/dump_stack.c:51 [<ffffffff818bdee6>] kmsan_report+0x276/0x2e0 mm/kmsan/kmsan.c:1008 [<ffffffff818bf0fb>] __msan_warning+0x5b/0xb0 mm/kmsan/kmsan_instr.c:424 [<ffffffff822dae71>] selinux_socket_bind+0xf41/0x1080 security/selinux/hooks.c:4288 [<ffffffff8229357c>] security_socket_bind+0x1ec/0x240 security/security.c:1240 [<ffffffff84265d98>] SYSC_bind+0x358/0x5f0 net/socket.c:1366 [<ffffffff84265a22>] SyS_bind+0x82/0xa0 net/socket.c:1356 [<ffffffff81005678>] do_syscall_64+0x58/0x70 arch/x86/entry/common.c:292 [<ffffffff8518217c>] entry_SYSCALL64_slow_path+0x25/0x25 arch/x86/entry/entry_64.o:? chained origin: 00000000ba6009bb [<ffffffff810bb7a7>] save_stack_trace+0x27/0x50 arch/x86/kernel/stacktrace.c:67 [< inline >] kmsan_save_stack_with_flags mm/kmsan/kmsan.c:322 [< inline >] kmsan_save_stack mm/kmsan/kmsan.c:337 [<ffffffff818bd2b8>] kmsan_internal_chain_origin+0x118/0x1e0 mm/kmsan/kmsan.c:530 [<ffffffff818bf033>] __msan_set_alloca_origin4+0xc3/0x130 mm/kmsan/kmsan_instr.c:380 [<ffffffff84265b69>] SYSC_bind+0x129/0x5f0 net/socket.c:1356 [<ffffffff84265a22>] SyS_bind+0x82/0xa0 net/socket.c:1356 [<ffffffff81005678>] do_syscall_64+0x58/0x70 arch/x86/entry/common.c:292 [<ffffffff8518217c>] return_from_SYSCALL_64+0x0/0x6a arch/x86/entry/entry_64.o:? origin description: ----address@SYSC_bind (origin=00000000b8c00900) ==================================================================
(the line numbers are relative to 4.8-rc6, but the bug persists upstream)
, when I run the following program as root:
======================================================= #include <string.h> #include <sys/socket.h> #include <netinet/in.h>
int main(int argc, char *argv[]) { struct sockaddr addr; int size = 0; if (argc > 1) { size = atoi(argv[1]); } memset(&addr, 0, sizeof(addr)); int fd = socket(PF_INET6, SOCK_DGRAM, IPPROTO_IP); bind(fd, &addr, size); return 0; } =======================================================
(for different values of |size| other error reports are printed).
This happens because bind() unconditionally copies |size| bytes of |addr| to the kernel, leaving the rest uninitialized. Then security_socket_bind() reads the IP address bytes, including the uninitialized ones, to determine the port, or e.g. pass them further to sel_netnode_find(), which uses them to calculate a hash.
Signed-off-by: Alexander Potapenko glider@google.com Acked-by: Eric Dumazet edumazet@google.com [PM: fixed some whitespace damage] Signed-off-by: Paul Moore paul@paul-moore.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- security/selinux/hooks.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index c2da45ae5b2a..b8278f3af9da 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -4328,10 +4328,18 @@ static int selinux_socket_bind(struct socket *sock, struct sockaddr *address, in u32 sid, node_perm;
if (family == PF_INET) { + if (addrlen < sizeof(struct sockaddr_in)) { + err = -EINVAL; + goto out; + } addr4 = (struct sockaddr_in *)address; snum = ntohs(addr4->sin_port); addrp = (char *)&addr4->sin_addr.s_addr; } else { + if (addrlen < SIN6_LEN_RFC2133) { + err = -EINVAL; + goto out; + } addr6 = (struct sockaddr_in6 *)address; snum = ntohs(addr6->sin6_port); addrp = (char *)&addr6->sin6_addr.s6_addr;