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authorAlexander Potapenko <glider@google.com>2017-03-01 12:57:20 +0100
committerDavid S. Miller <davem@davemloft.net>2017-03-01 20:55:57 -0800
commit540e2894f7905538740aaf122bd8e0548e1c34a4 (patch)
tree6be18e807c044ba2a342c0a965bebfa426733f18
parent8953de2f02ad7b15e4964c82f9afd60f128e4e98 (diff)
downloadlinux-540e2894f7905538740aaf122bd8e0548e1c34a4.tar.gz
net: don't call strlen() on the user buffer in packet_bind_spkt()
KMSAN (KernelMemorySanitizer, a new error detection tool) reports use of uninitialized memory in packet_bind_spkt(): Acked-by: Eric Dumazet <edumazet@google.com> ================================================================== BUG: KMSAN: use of unitialized memory CPU: 0 PID: 1074 Comm: packet Not tainted 4.8.0-rc6+ #1891 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 0000000000000000 ffff88006b6dfc08 ffffffff82559ae8 ffff88006b6dfb48 ffffffff818a7c91 ffffffff85b9c870 0000000000000092 ffffffff85b9c550 0000000000000000 0000000000000092 00000000ec400911 0000000000000002 Call Trace: [< inline >] __dump_stack lib/dump_stack.c:15 [<ffffffff82559ae8>] dump_stack+0x238/0x290 lib/dump_stack.c:51 [<ffffffff818a6626>] kmsan_report+0x276/0x2e0 mm/kmsan/kmsan.c:1003 [<ffffffff818a783b>] __msan_warning+0x5b/0xb0 mm/kmsan/kmsan_instr.c:424 [< inline >] strlen lib/string.c:484 [<ffffffff8259b58d>] strlcpy+0x9d/0x200 lib/string.c:144 [<ffffffff84b2eca4>] packet_bind_spkt+0x144/0x230 net/packet/af_packet.c:3132 [<ffffffff84242e4d>] SYSC_bind+0x40d/0x5f0 net/socket.c:1370 [<ffffffff84242a22>] SyS_bind+0x82/0xa0 net/socket.c:1356 [<ffffffff8515991b>] entry_SYSCALL_64_fastpath+0x13/0x8f arch/x86/entry/entry_64.o:? chained origin: 00000000eba00911 [<ffffffff810bb787>] 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:334 [<ffffffff818a59f8>] kmsan_internal_chain_origin+0x118/0x1e0 mm/kmsan/kmsan.c:527 [<ffffffff818a7773>] __msan_set_alloca_origin4+0xc3/0x130 mm/kmsan/kmsan_instr.c:380 [<ffffffff84242b69>] SYSC_bind+0x129/0x5f0 net/socket.c:1356 [<ffffffff84242a22>] SyS_bind+0x82/0xa0 net/socket.c:1356 [<ffffffff8515991b>] entry_SYSCALL_64_fastpath+0x13/0x8f arch/x86/entry/entry_64.o:? origin description: ----address@SYSC_bind (origin=00000000eb400911) ================================================================== (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 <netpacket/packet.h> #include <net/ethernet.h> int main() { struct sockaddr addr; memset(&addr, 0xff, sizeof(addr)); addr.sa_family = AF_PACKET; int fd = socket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ALL)); bind(fd, &addr, sizeof(addr)); return 0; } ===================================== This happens because addr.sa_data copied from the userspace is not zero-terminated, and copying it with strlcpy() in packet_bind_spkt() results in calling strlen() on the kernel copy of that non-terminated buffer. Signed-off-by: Alexander Potapenko <glider@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/packet/af_packet.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 2bd0d19..a0dbe7c 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3103,7 +3103,7 @@ static int packet_bind_spkt(struct socket *sock, struct sockaddr *uaddr,
int addr_len)
{
struct sock *sk = sock->sk;
- char name[15];
+ char name[sizeof(uaddr->sa_data) + 1];
/*
* Check legality
@@ -3111,7 +3111,11 @@ static int packet_bind_spkt(struct socket *sock, struct sockaddr *uaddr,
if (addr_len != sizeof(struct sockaddr))
return -EINVAL;
- strlcpy(name, uaddr->sa_data, sizeof(name));
+ /* uaddr->sa_data comes from the userspace, it's not guaranteed to be
+ * zero-terminated.
+ */
+ memcpy(name, uaddr->sa_data, sizeof(uaddr->sa_data));
+ name[sizeof(uaddr->sa_data)] = 0;
return packet_do_bind(sk, name, 0, pkt_sk(sk)->num);
}