From bc5d31d71815dcb90dcd1e07954db9116ff032bc Mon Sep 17 00:00:00 2001 From: Yi Yang Date: Tue, 26 Dec 2023 03:40:55 +0000 Subject: [PATCH] tty: n_gsm: fix the UAF caused by race condition in gsm_cleanup_mux stable inclusion from stable-v5.10.192 commit 869ce5e5984595bd2c62b598d977debc218b6f4d category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I8QFUO CVE: CVE-2023-6546 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=869ce5e5984595bd2c62b598d977debc218b6f4d -------------------------------- commit 3c4f8333b582487a2d1e02171f1465531cde53e3 upstream. In commit 9b9c8195f3f0 ("tty: n_gsm: fix UAF in gsm_cleanup_mux"), the UAF problem is not completely fixed. There is a race condition in gsm_cleanup_mux(), which caused this UAF. The UAF problem is triggered by the following race: task[5046] task[5054] ----------------------- ----------------------- gsm_cleanup_mux(); dlci = gsm->dlci[0]; mutex_lock(&gsm->mutex); gsm_cleanup_mux(); dlci = gsm->dlci[0]; //Didn't take the lock gsm_dlci_release(gsm->dlci[i]); gsm->dlci[i] = NULL; mutex_unlock(&gsm->mutex); mutex_lock(&gsm->mutex); dlci->dead = true; //UAF Fix it by assigning values after mutex_lock(). Link: https://syzkaller.appspot.com/text?tag=CrashReport&x=176188b5a80000 Cc: stable Fixes: 9b9c8195f3f0 ("tty: n_gsm: fix UAF in gsm_cleanup_mux") Fixes: aa371e96f05d ("tty: n_gsm: fix restart handling via CLD command") Signed-off-by: Yi Yang Co-developed-by: Qiumiao Zhang Signed-off-by: Qiumiao Zhang Link: https://lore.kernel.org/r/20230811031121.153237-1-yiyang13@huawei.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Yi Yang (cherry picked from commit 514791dd0524a3907eb64997b661d4c9efa646f9) --- drivers/tty/n_gsm.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 23b014b8c919..3693ad9f4521 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -2159,12 +2159,13 @@ static void gsm_error(struct gsm_mux *gsm, static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc) { int i; - struct gsm_dlci *dlci = gsm->dlci[0]; + struct gsm_dlci *dlci; struct gsm_msg *txq, *ntxq; gsm->dead = true; mutex_lock(&gsm->mutex); + dlci = gsm->dlci[0]; if (dlci) { if (disc && dlci->state != DLCI_CLOSED) { gsm_dlci_begin_close(dlci); -- Gitee