From: Qu Wenruo <wqu@suse.com>
To: linux-btrfs@vger.kernel.org
Cc: butt3rflyh4ck <butterflyhuangxx@gmail.com>
Subject: [PATCH] btrfs: fix NULL pointer dereference when deleting device by invalid id
Date: Fri, 6 Aug 2021 18:24:15 +0800 [thread overview]
Message-ID: <20210806102415.304717-1-wqu@suse.com> (raw)
[BUG]
It's super easy to trigger NULL pointer dereference, just by removing a
non-exist device id:
# mkfs.btrfs -f -m single -d single /dev/test/scratch1 \
/dev/test/scratch2
# mount /dev/test/scratch1 /mnt/btrfs
# btrfs device remove 3 /mnt/btrfs
Then we have the following kernel NULL pointer dereference:
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP NOPTI
CPU: 9 PID: 649 Comm: btrfs Not tainted 5.14.0-rc3-custom+ #35
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:btrfs_rm_device+0x4de/0x6b0 [btrfs]
btrfs_ioctl+0x18bb/0x3190 [btrfs]
? lock_is_held_type+0xa5/0x120
? find_held_lock.constprop.0+0x2b/0x80
? do_user_addr_fault+0x201/0x6a0
? lock_release+0xd2/0x2d0
? __x64_sys_ioctl+0x83/0xb0
__x64_sys_ioctl+0x83/0xb0
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae
[CAUSE]
Commit a27a94c2b0c7 ("btrfs: Make btrfs_find_device_by_devspec return
btrfs_device directly") moves the "missing" device path check into
btrfs_rm_device().
But btrfs_rm_device() itself can have case where it only receives
@devid, with NULL as @device_path.
In that case, calling strcmp() on NULL will trigger the NULL pointer
dereference.
Before that commit, we handle the "missing" case inside
btrfs_find_device_by_devspec(), which will not check @device_path at all
if @devid is provided, thus no way to trigger the bug.
[FIX]
Before calling strcmp(), also make sure @device_path is not NULL.
Fixes: a27a94c2b0c7 ("btrfs: Make btrfs_find_device_by_devspec return btrfs_device directly")
Reported-by: butt3rflyh4ck <butterflyhuangxx@gmail.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
fs/btrfs/volumes.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 230192d097c4..5156254a9655 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2079,7 +2079,7 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path,
if (IS_ERR(device)) {
if (PTR_ERR(device) == -ENOENT &&
- strcmp(device_path, "missing") == 0)
+ device_path && strcmp(device_path, "missing") == 0)
ret = BTRFS_ERROR_DEV_MISSING_NOT_FOUND;
else
ret = PTR_ERR(device);
--
2.32.0
next reply other threads:[~2021-08-06 10:24 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-06 10:24 Qu Wenruo [this message]
2021-08-10 14:23 ` [PATCH] btrfs: fix NULL pointer dereference when deleting device by invalid id David Sterba
2021-08-10 15:57 ` Anand Jain
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210806102415.304717-1-wqu@suse.com \
--to=wqu@suse.com \
--cc=butterflyhuangxx@gmail.com \
--cc=linux-btrfs@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).