From: Sungmin Kang <726ksm@gmail.com> Date: Sat, 18 Jul 2026 07:36:30 +0000 (+0900) Subject: net: slip: serialize receive against buffer reallocation X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=ee7f9bb9320add61f7b367d7e6cd55e3a3a4d65d;p=thirdparty%2Fkernel%2Flinux.git net: slip: serialize receive against buffer reallocation sl_realloc_bufs() replaces rbuff and updates buffsize while holding sl->lock. slip_receive_buf() reads those fields and writes through rbuff without holding the lock. An MTU change can therefore race with receive processing. An MTU shrink can expose the new smaller rbuff with the old larger bound, causing an out-of-bounds write. A receive callback which already loaded the old rbuff can instead continue writing after that buffer has been freed. Serialize receive processing with sl_realloc_bufs() by holding sl->lock while consuming each receive batch. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Sungmin Kang <726ksm@gmail.com> Link: https://patch.msgid.link/20260718073631.1674-1-726ksm@gmail.com Signed-off-by: Jakub Kicinski --- diff --git a/drivers/net/slip/slip.c b/drivers/net/slip/slip.c index 820e1a8fc9560..faae711cf793d 100644 --- a/drivers/net/slip/slip.c +++ b/drivers/net/slip/slip.c @@ -693,6 +693,8 @@ static void slip_receive_buf(struct tty_struct *tty, const u8 *cp, const u8 *fp, if (!sl || sl->magic != SLIP_MAGIC || !netif_running(sl->dev)) return; + spin_lock_bh(&sl->lock); + /* Read the characters out of the buffer */ while (count--) { if (fp && *fp++) { @@ -708,6 +710,8 @@ static void slip_receive_buf(struct tty_struct *tty, const u8 *cp, const u8 *fp, #endif slip_unesc(sl, *cp++); } + + spin_unlock_bh(&sl->lock); } /************************************