btrfs: fix use-after-free of block device file in __btrfs_free_extra_devids()
Subsystems (2)
PATCH 1/1 btrfs: fix use-after-free of block device file in __btrfs_free_extra_devids()
From: Zhihao Cheng <[email protected]>
commit aec8e6bf839101784f3ef037dcdb9432c3f32343 ("btrfs:
fix use-after-free of block device file in __btrfs_free_extra_devids()")
Mounting btrfs from two images (which have the same one fsid and two different dev_uuids) in certain executing order may trigger an UAF for variable 'device->bdev_file' in __btrfs_free_extra_devids(). And following are the details:
1. Attach image_1 to loop0, attach image_2 to loop1, and scan btrfs devices by ioctl(BTRFS_IOC_SCAN_DEV):
/ btrfs_device_1 → loop0
fs_device
\ btrfs_device_2 → loop1
2. mount /dev/loop0 /mnt
btrfs_open_devices
btrfs_device_1->bdev_file = btrfs_get_bdev_and_sb(loop0)
btrfs_device_2->bdev_file = btrfs_get_bdev_and_sb(loop1)
btrfs_fill_super
open_ctree
fail: btrfs_close_devices // -ENOMEM
btrfs_close_bdev(btrfs_device_1)
fput(btrfs_device_1->bdev_file)
// btrfs_device_1->bdev_file is freed
btrfs_close_bdev(btrfs_device_2)
fput(btrfs_device_2->bdev_file)3. mount /dev/loop1 /mnt
btrfs_open_devices
btrfs_get_bdev_and_sb(&bdev_file)
// EIO, btrfs_device_1->bdev_file is not assigned,
// which points to a freed memory area
btrfs_device_2->bdev_file = btrfs_get_bdev_and_sb(loop1)
btrfs_fill_super
open_ctree
btrfs_free_extra_devids
if (btrfs_device_1->bdev_file)
fput(btrfs_device_1->bdev_file) // UAF !Fix it by setting 'device->bdev_file' as 'NULL' after closing the btrfs_device in btrfs_close_one_device().
--- fs/btrfs/volumes.c | 1 + 1 file changed, 1 insertion(+)
fs/btrfs/volumes.c +1 -0
@@ -1176,6 +1176,7 @@ static void btrfs_close_one_device(struct btrfs_device *device)if (device->bdev) { fs_devices->open_devices--; device->bdev =NULL ; + device->bdev_file =NULL ; }clear_bit (BTRFS_DEV_STATE_WRITEABLE , &device->dev_state);btrfs_destroy_dev_zone_info (device);
Signature · 1 line
2.35.6
Hi Shubham,
Quoted 61 lines · Shubham Pushpkar
From: Zhihao Cheng <[email protected]>
commit
aec8e6bf839101784f3ef037dcdb9432c3f32343("btrfs:
fix use-after-free of block device file in__btrfs_free_extra_devids()")Mounting btrfs from two images (which have the same one fsid and two different
dev_uuids) in certain executing order may trigger an UAF for variable 'device->bdev_file' in__btrfs_free_extra_devids(). And following are the details:1. Attach
image_1to loop0, attachimage_2to loop1, and scan btrfs devices byioctl(BTRFS_IOC_SCAN_DEV):/
btrfs_device_1→ loop0
fs_device
\btrfs_device_2→ loop1
2. mount/dev/loop0/mntbtrfs_open_devices btrfs_device_1->bdev_file = btrfs_get_bdev_and_sb(loop0) btrfs_device_2->bdev_file = btrfs_get_bdev_and_sb(loop1) btrfs_fill_super open_ctree fail: btrfs_close_devices // -ENOMEM btrfs_close_bdev(btrfs_device_1) fput(btrfs_device_1->bdev_file) // btrfs_device_1->bdev_file is freed btrfs_close_bdev(btrfs_device_2) fput(btrfs_device_2->bdev_file)3. mount
/dev/loop1/mntbtrfs_open_devices btrfs_get_bdev_and_sb(&bdev_file) // EIO, btrfs_device_1->bdev_file is not assigned, // which points to a freed memory area btrfs_device_2->bdev_file = btrfs_get_bdev_and_sb(loop1) btrfs_fill_super open_ctree btrfs_free_extra_devids if (btrfs_device_1->bdev_file) fput(btrfs_device_1->bdev_file) // UAF !Fix it by setting '
device->bdev_file' as 'NULL' after closing thebtrfs_deviceinbtrfs_close_one_device().Fixes 142388194191 ("btrfs: do not background blkdev_put()")CC [email protected] # 4.19+Signed-off-by Zhihao Cheng <[email protected]>Reviewed-by David Sterba <[email protected]>Signed-off-by David Sterba <[email protected]>(cherry picked from commit aec8e6bf839101784f3ef037dcdb9432c3f32343)Signed-off-by Shubham Pushpkar <[email protected]>--- fs/btrfs/volumes.c | 1 + 1 file changed, 1 insertion(+)fs/btrfs/volumes.c +0
-0
fs/btrfs/volumes.c static void btrfs_close_one_device(struct btrfs_device *device) · line 1179
Quoted 4 lines
fs/btrfs/volumes.c +1
-0@@ -1176,6 +1176,7 @@ static void btrfs_close_one_device(struct btrfs_device *device)if (device->bdev) { fs_devices->open_devices--; device->bdev =NULL ; + device->bdev_file =NULL ;
Looks bad.
"bdev_file" is not a member of struct btrfs_device in 6.6.y. It is added only in commit: 9ae061cf2a46 ("btrfs: port device access to file") which is not in 6.6.y
Hint: This has CC:stable and Fixes tag and a clean cherry-pick so there should be a reason why this didn't get into stable easily.(reason in this case in build failure)
Thanks,
Harshit
Quoted 3 lines
fs/btrfs/volumes.c +0
-0}clear_bit (BTRFS_DEV_STATE_WRITEABLE , &device->dev_state);btrfs_destroy_dev_zone_info (device);
[ Sasha's backport helper bot ]
Hi,
Found matching upstream commit: aec8e6bf839101784f3ef037dcdb9432c3f32343
WARNING: Author mismatch between patch and found commit:
Backport author: Shubham Pushpkar<[email protected]> Commit author: Zhihao Cheng<[email protected]>
Status in newer kernel trees:
6.13.y | Present (exact SHA1)
6.12.y | Present (exact SHA1)
6.6.y | Not found
Note: The patch differs from the upstream commit:
---
1: aec8e6bf83910 ! 1: afbc8c0c36536 btrfs: fix use-after-free of block device file in __btrfs_free_extra_devids()
@@ Metadata
## Commit message ##
btrfs: fix use-after-free of block device file in __btrfs_free_extra_devids()
+ commit aec8e6bf839101784f3ef037dcdb9432c3f32343 ("btrfs:
+ fix use-after-free of block device file in __btrfs_free_extra_devids()")
+
Mounting btrfs from two images (which have the same one fsid and two different dev_uuids) in certain executing order may trigger an UAF for variable 'device->bdev_file' in __btrfs_free_extra_devids(). And
@@ Commit message
+ (cherry picked from commit aec8e6bf839101784f3ef037dcdb9432c3f32343)
+ Signed-off-by: Shubham Pushpkar <[email protected]>
## fs/btrfs/volumes.c ##
@@ fs/btrfs/volumes.c: static void btrfs_close_one_device(struct btrfs_device *device)
---
Results of testing on various branches:
| Branch | Patch Apply | Build Test | |---------------------------|-------------|------------| | stable/linux-6.6.y | Success | Failed |
Build Errors:
Build error for stable/linux-6.6.y:
lib/test_dhry.o: warning: objtool: dhry() falls through to next function dhry_run_set.cold() fs/btrfs/volumes.c: In function 'btrfs_close_one_device':
fs/btrfs/volumes.c:1179:23: error: 'struct btrfs_device' has no member named 'bdev_file'
1179 | device->bdev_file = NULL;
| ^~
make[4]: *** [scripts/Makefile.build:243: fs/btrfs/volumes.o] Error 1 make[4]: Target 'fs/btrfs/' not remade because of errors.
make[3]: *** [scripts/Makefile.build:480: fs/btrfs] Error 2
make[3]: Target 'fs/' not remade because of errors.
make[2]: *** [scripts/Makefile.build:480: fs] Error 2
make[2]: Target './' not remade because of errors.
make[1]: *** [/home/sasha/build/linus-next/Makefile:1921: .] Error 2 make[1]: Target '__all' not remade because of errors.
make: *** [Makefile:234: __sub-make] Error 2
make: Target '__all' not remade because of errors.