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net: slip: serialize receive against buffer reallocation

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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: 1da177e4c3 ("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 <kuba@kernel.org>
This commit is contained in:
Sungmin Kang 2026-07-18 16:36:30 +09:00 committed by Jakub Kicinski
parent 7fd55911fd
commit ee7f9bb932
1 changed files with 4 additions and 0 deletions
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4
drivers/net/slip/slip.c
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@ -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);
}
/************************************