From 9b9c8195f3f0d74a826077fc1c01b9ee74907239 Mon Sep 17 00:00:00 2001
From: Chaoyuan Peng <hedonistsmith@gmail.com>
Date: Tue, 18 Jul 2023 04:39:43 +0000
Subject: [PATCH] tty: n_gsm: fix UAF in gsm_cleanup_mux
Git-commit: 9b9c8195f3f0d74a826077fc1c01b9ee74907239
Patch-mainline: v6.5-rc4
References: git-fixes
In gsm_cleanup_mux() the 'gsm->dlci' pointer was not cleaned properly,
leaving it a dangling pointer after gsm_dlci_release.
This leads to use-after-free where 'gsm->dlci[0]' are freed and accessed
by the subsequent gsm_cleanup_mux().
Such is the case in the following call trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
print_address_description+0x63/0x3b0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:434 [inline]
kasan_report+0x16b/0x1c0 mm/kasan/report.c:451
gsm_cleanup_mux+0x76a/0x850 drivers/tty/n_gsm.c:2397
gsm_config drivers/tty/n_gsm.c:2653 [inline]
gsmld_ioctl+0xaae/0x15b0 drivers/tty/n_gsm.c:2986
tty_ioctl+0x8ff/0xc50 drivers/tty/tty_io.c:2816
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xf1/0x160 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x61/0xcb
</TASK>
Allocated by task 3501:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
____kasan_kmalloc+0xba/0xf0 mm/kasan/common.c:513
kasan_kmalloc include/linux/kasan.h:264 [inline]
kmem_cache_alloc_trace+0x143/0x290 mm/slub.c:3247
kmalloc include/linux/slab.h:591 [inline]
kzalloc include/linux/slab.h:721 [inline]
gsm_dlci_alloc+0x53/0x3a0 drivers/tty/n_gsm.c:1932
gsm_activate_mux+0x1c/0x330 drivers/tty/n_gsm.c:2438
gsm_config drivers/tty/n_gsm.c:2677 [inline]
gsmld_ioctl+0xd46/0x15b0 drivers/tty/n_gsm.c:2986
tty_ioctl+0x8ff/0xc50 drivers/tty/tty_io.c:2816
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xf1/0x160 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x61/0xcb
Freed by task 3501:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x4b/0x80 mm/kasan/common.c:46
kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
____kasan_slab_free+0xd8/0x120 mm/kasan/common.c:366
kasan_slab_free include/linux/kasan.h:230 [inline]
slab_free_hook mm/slub.c:1705 [inline]
slab_free_freelist_hook+0xdd/0x160 mm/slub.c:1731
slab_free mm/slub.c:3499 [inline]
kfree+0xf1/0x270 mm/slub.c:4559
dlci_put drivers/tty/n_gsm.c:1988 [inline]
gsm_dlci_release drivers/tty/n_gsm.c:2021 [inline]
gsm_cleanup_mux+0x574/0x850 drivers/tty/n_gsm.c:2415
gsm_config drivers/tty/n_gsm.c:2653 [inline]
gsmld_ioctl+0xaae/0x15b0 drivers/tty/n_gsm.c:2986
tty_ioctl+0x8ff/0xc50 drivers/tty/tty_io.c:2816
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xf1/0x160 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x61/0xcb
Fixes: aa371e96f05d ("tty: n_gsm: fix restart handling via CLD command")
Signed-off-by: Chaoyuan Peng <hedonistsmith@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/tty/n_gsm.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index b411a26cc092..1cdefac4dd1b 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -3070,8 +3070,10 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
gsm->has_devices = false;
}
for (i = NUM_DLCI - 1; i >= 0; i--)
- if (gsm->dlci[i])
+ if (gsm->dlci[i]) {
gsm_dlci_release(gsm->dlci[i]);
+ gsm->dlci[i] = NULL;
+ }
mutex_unlock(&gsm->mutex);
/* Now wipe the queues */
tty_ldisc_flush(gsm->tty);
--
2.35.3