From: Mashiro Chen Date: Tue, 7 Apr 2026 17:31:01 +0000 (+0800) Subject: net: hamradio: 6pack: fix uninit-value in sixpack_receive_buf X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=bf9a38803b2626b01cc769aaf13485d8650f576f;p=thirdparty%2Fkernel%2Flinux.git net: hamradio: 6pack: fix uninit-value in sixpack_receive_buf sixpack_receive_buf() does not properly skip bytes with TTY error flags. The while loop iterates through the flags buffer but never advances the data pointer (cp), and passes the original count (including error bytes) to sixpack_decode(). This causes sixpack_decode() to process bytes that should have been skipped due to TTY errors. The TTY layer does not guarantee that cp[i] holds a meaningful value when fp[i] is set, so passing those positions to sixpack_decode() results in KMSAN reporting an uninit-value read. Fix this by processing bytes one at a time, advancing cp on each iteration, and only passing valid (non-error) bytes to sixpack_decode(). This matches the pattern used by slip_receive_buf() and mkiss_receive_buf() for the same purpose. Reported-by: syzbot+ecdb8c9878a81eb21e54@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=ecdb8c9878a81eb21e54 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Mashiro Chen Reviewed-by: Simon Horman Link: https://patch.msgid.link/20260407173101.107352-1-mashiro.chen@mailbox.org Signed-off-by: Jakub Kicinski --- diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c index 885992951e8a6..c8b2dc5c1becc 100644 --- a/drivers/net/hamradio/6pack.c +++ b/drivers/net/hamradio/6pack.c @@ -391,7 +391,6 @@ static void sixpack_receive_buf(struct tty_struct *tty, const u8 *cp, const u8 *fp, size_t count) { struct sixpack *sp; - size_t count1; if (!count) return; @@ -401,16 +400,16 @@ static void sixpack_receive_buf(struct tty_struct *tty, const u8 *cp, return; /* Read the characters out of the buffer */ - count1 = count; - while (count) { - count--; + while (count--) { if (fp && *fp++) { if (!test_and_set_bit(SIXPF_ERROR, &sp->flags)) sp->dev->stats.rx_errors++; + cp++; continue; } + sixpack_decode(sp, cp, 1); + cp++; } - sixpack_decode(sp, cp, count1); tty_unthrottle(tty); }