diff mbox series

[net,v2] ipv4: Fix uninit-value access in __ip_make_skb()

Message ID 20240430123945.2057348-1-syoshida@redhat.com (mailing list archive)
State Accepted
Commit fc1092f51567277509563800a3c56732070b6aa4
Delegated to: Netdev Maintainers
Headers show
Series [net,v2] ipv4: Fix uninit-value access in __ip_make_skb() | expand

Checks

Context Check Description
netdev/series_format success Single patches do not need cover letters
netdev/tree_selection success Clearly marked for net
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag present in non-next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 928 this patch: 928
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers fail 2 blamed authors not CCed: william.xuanziyang@huawei.com willemb@google.com; 2 maintainers not CCed: william.xuanziyang@huawei.com willemb@google.com
netdev/build_clang success Errors and warnings before: 938 this patch: 938
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 939 this patch: 939
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 17 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-05-01--06-00 (tests: 997)

Commit Message

Shigeru Yoshida April 30, 2024, 12:39 p.m. UTC
KMSAN reported uninit-value access in __ip_make_skb() [1].  __ip_make_skb()
tests HDRINCL to know if the skb has icmphdr. However, HDRINCL can cause a
race condition. If calling setsockopt(2) with IP_HDRINCL changes HDRINCL
while __ip_make_skb() is running, the function will access icmphdr in the
skb even if it is not included. This causes the issue reported by KMSAN.

Check FLOWI_FLAG_KNOWN_NH on fl4->flowi4_flags instead of testing HDRINCL
on the socket.

Also, fl4->fl4_icmp_type and fl4->fl4_icmp_code are not initialized. These
are union in struct flowi4 and are implicitly initialized by
flowi4_init_output(), but we should not rely on specific union layout.

Initialize these explicitly in raw_sendmsg().

[1]
BUG: KMSAN: uninit-value in __ip_make_skb+0x2b74/0x2d20 net/ipv4/ip_output.c:1481
 __ip_make_skb+0x2b74/0x2d20 net/ipv4/ip_output.c:1481
 ip_finish_skb include/net/ip.h:243 [inline]
 ip_push_pending_frames+0x4c/0x5c0 net/ipv4/ip_output.c:1508
 raw_sendmsg+0x2381/0x2690 net/ipv4/raw.c:654
 inet_sendmsg+0x27b/0x2a0 net/ipv4/af_inet.c:851
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x274/0x3c0 net/socket.c:745
 __sys_sendto+0x62c/0x7b0 net/socket.c:2191
 __do_sys_sendto net/socket.c:2203 [inline]
 __se_sys_sendto net/socket.c:2199 [inline]
 __x64_sys_sendto+0x130/0x200 net/socket.c:2199
 do_syscall_64+0xd8/0x1f0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:3804 [inline]
 slab_alloc_node mm/slub.c:3845 [inline]
 kmem_cache_alloc_node+0x5f6/0xc50 mm/slub.c:3888
 kmalloc_reserve+0x13c/0x4a0 net/core/skbuff.c:577
 __alloc_skb+0x35a/0x7c0 net/core/skbuff.c:668
 alloc_skb include/linux/skbuff.h:1318 [inline]
 __ip_append_data+0x49ab/0x68c0 net/ipv4/ip_output.c:1128
 ip_append_data+0x1e7/0x260 net/ipv4/ip_output.c:1365
 raw_sendmsg+0x22b1/0x2690 net/ipv4/raw.c:648
 inet_sendmsg+0x27b/0x2a0 net/ipv4/af_inet.c:851
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x274/0x3c0 net/socket.c:745
 __sys_sendto+0x62c/0x7b0 net/socket.c:2191
 __do_sys_sendto net/socket.c:2203 [inline]
 __se_sys_sendto net/socket.c:2199 [inline]
 __x64_sys_sendto+0x130/0x200 net/socket.c:2199
 do_syscall_64+0xd8/0x1f0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

CPU: 1 PID: 15709 Comm: syz-executor.7 Not tainted 6.8.0-11567-gb3603fcb79b1 #25
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-1.fc39 04/01/2014

Fixes: 99e5acae193e ("ipv4: Fix potential uninit variable access bug in __ip_make_skb()")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
---
v1->v2: https://lore.kernel.org/all/20240324050554.1609460-1-syoshida@redhat.com/
- Explicitly initialize fl4->fl4_icmp_type and fl4->fl4_icmp_code because
  we should not rely on a specific union layout.
---
 net/ipv4/ip_output.c | 2 +-
 net/ipv4/raw.c       | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

Comments

patchwork-bot+netdevbpf@kernel.org May 2, 2024, 8:20 a.m. UTC | #1
Hello:

This patch was applied to netdev/net.git (main)
by Paolo Abeni <pabeni@redhat.com>:

On Tue, 30 Apr 2024 21:39:45 +0900 you wrote:
> KMSAN reported uninit-value access in __ip_make_skb() [1].  __ip_make_skb()
> tests HDRINCL to know if the skb has icmphdr. However, HDRINCL can cause a
> race condition. If calling setsockopt(2) with IP_HDRINCL changes HDRINCL
> while __ip_make_skb() is running, the function will access icmphdr in the
> skb even if it is not included. This causes the issue reported by KMSAN.
> 
> Check FLOWI_FLAG_KNOWN_NH on fl4->flowi4_flags instead of testing HDRINCL
> on the socket.
> 
> [...]

Here is the summary with links:
  - [net,v2] ipv4: Fix uninit-value access in __ip_make_skb()
    https://git.kernel.org/netdev/net/c/fc1092f51567

You are awesome, thank you!
diff mbox series

Patch

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 1fe794967211..39229fd0601a 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1473,7 +1473,7 @@  struct sk_buff *__ip_make_skb(struct sock *sk,
 		 * by icmp_hdr(skb)->type.
 		 */
 		if (sk->sk_type == SOCK_RAW &&
-		    !inet_test_bit(HDRINCL, sk))
+		    !(fl4->flowi4_flags & FLOWI_FLAG_KNOWN_NH))
 			icmp_type = fl4->fl4_icmp_type;
 		else
 			icmp_type = icmp_hdr(skb)->type;
diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index dcb11f22cbf2..4cb43401e0e0 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -612,6 +612,9 @@  static int raw_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 			    (hdrincl ? FLOWI_FLAG_KNOWN_NH : 0),
 			   daddr, saddr, 0, 0, sk->sk_uid);
 
+	fl4.fl4_icmp_type = 0;
+	fl4.fl4_icmp_code = 0;
+
 	if (!hdrincl) {
 		rfv.msg = msg;
 		rfv.hlen = 0;