2022-03-03 22:21:20

by Dongliang Mu

Subject: [PATCH] btrfs: don't access possibly stale fs_info data in device_list_add

From: Dongliang Mu <[email protected]>

Syzbot reported a possible use-after-free in printing information
in device_list_add.

Very similar with the bug fixed by commit 0697d9a61099 ("btrfs: don't
access possibly stale fs_info data for printing duplicate device"),
but this time the use occurs in btrfs_info_in_rcu.

============================================================
Call Trace:
kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
btrfs_printk+0x395/0x425 fs/btrfs/super.c:244
device_list_add.cold+0xd7/0x2ed fs/btrfs/volumes.c:957
btrfs_scan_one_device+0x4c7/0x5c0 fs/btrfs/volumes.c:1387
btrfs_control_ioctl+0x12a/0x2d0 fs/btrfs/super.c:2409
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
============================================================

Fix this by modifying device->fs_info to NULL too.

Reported-and-tested-by: [email protected]
Signed-off-by: Dongliang Mu <[email protected]>
---
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 b07d382d53a8..c1325bdae9a1 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -954,7 +954,7 @@ static noinline struct btrfs_device *device_list_add(const char *path,
task_pid_nr(current));
return ERR_PTR(-EEXIST);
}
- btrfs_info_in_rcu(device->fs_info,
+ btrfs_info_in_rcu(NULL,
"devid %llu device path %s changed to %s scanned by %s (%d)",
devid, rcu_str_deref(device->name),
path, current->comm,
--
2.25.1

2022-03-04 19:41:03

by David Sterba

Subject: Re: [PATCH] btrfs: don't access possibly stale fs_info data in device_list_add

On Thu, Mar 03, 2022 at 10:40:27PM +0800, Dongliang Mu wrote:
> From: Dongliang Mu <[email protected]>
>
> Syzbot reported a possible use-after-free in printing information
> in device_list_add.
>
> Very similar with the bug fixed by commit 0697d9a61099 ("btrfs: don't
> access possibly stale fs_info data for printing duplicate device"),
> but this time the use occurs in btrfs_info_in_rcu.
>
> ============================================================
> Call Trace:
> kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
> btrfs_printk+0x395/0x425 fs/btrfs/super.c:244
> device_list_add.cold+0xd7/0x2ed fs/btrfs/volumes.c:957
> btrfs_scan_one_device+0x4c7/0x5c0 fs/btrfs/volumes.c:1387
> btrfs_control_ioctl+0x12a/0x2d0 fs/btrfs/super.c:2409
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:874 [inline]
> __se_sys_ioctl fs/ioctl.c:860 [inline]
> __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> ============================================================
>
> Fix this by modifying device->fs_info to NULL too.
>
> Reported-and-tested-by: [email protected]
> Signed-off-by: Dongliang Mu <[email protected]>

Added to misc-next, thanks.