diff mbox series

[net-next,v1,1/1] ppp: Fix KMSAN warning by initializing 2-byte header

Message ID 20250218133145.265313-2-jiayuan.chen@linux.dev (mailing list archive)
State New
Delegated to: Netdev Maintainers
Headers show
Series ppp: Fix KMSAN uninit-value warning | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 9 of 9 maintainers
netdev/build_clang success Errors and warnings before: 0 this patch: 0
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 No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/checkpatch warning WARNING: The commit message has 'syzkaller', perhaps it also needs a 'Fixes:' tag?
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 fail net-next-2025-02-18--18-00 (tests: 891)

Commit Message

Jiayuan Chen Feb. 18, 2025, 1:31 p.m. UTC 
The ppp program adds a 2-byte pseudo-header for socket filters, which is
normally skipped by regular BPF programs, causing no issues.

However, for abnormal BPF programs that use these uninitialized 2 bytes,
a KMSAN warning is triggered.

Reported-by: syzbot+853242d9c9917165d791@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/bpf/000000000000dea025060d6bc3bc@google.com/
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
---
 drivers/net/ppp/ppp_generic.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index 4583e15ad03a..a913403d5847 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -1765,7 +1765,7 @@  ppp_send_frame(struct ppp *ppp, struct sk_buff *skb)
 		/* check if we should pass this packet */
 		/* the filter instructions are constructed assuming
 		   a four-byte PPP header on each packet */
-		*(u8 *)skb_push(skb, 2) = 1;
+		*(u16 *)skb_push(skb, 2) = 1;
 		if (ppp->pass_filter &&
 		    bpf_prog_run(ppp->pass_filter, skb) == 0) {
 			if (ppp->debug & 1)
@@ -2489,7 +2489,7 @@  ppp_receive_nonmp_frame(struct ppp *ppp, struct sk_buff *skb)
 			if (skb_unclone(skb, GFP_ATOMIC))
 				goto err;
 
-			*(u8 *)skb_push(skb, 2) = 0;
+			*(u16 *)skb_push(skb, 2) = 0;
 			if (ppp->pass_filter &&
 			    bpf_prog_run(ppp->pass_filter, skb) == 0) {
 				if (ppp->debug & 1)