6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Qu Wenruo <wqu@xxxxxxxx>
commit 10d9d8c3512f16cad47b2ff81ec6fc4b27d8ee10 upstream.
[BUG]
There is an internal report that KASAN is reporting use-after-free, with
the following backtrace:
BUG: KASAN: slab-use-after-free in btrfs_check_read_bio+0xa68/0xb70 [btrfs]
Read of size 4 at addr ffff8881117cec28 by task kworker/u16:2/45
CPU: 1 UID: 0 PID: 45 Comm: kworker/u16:2 Not tainted 6.11.0-rc2-next-20240805-default+ #76
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-3-gd478f380-rebuilt.opensuse.org 04/01/2014
Workqueue: btrfs-endio btrfs_end_bio_work [btrfs]
Call Trace:
dump_stack_lvl+0x61/0x80
print_address_description.constprop.0+0x5e/0x2f0
print_report+0x118/0x216
kasan_report+0x11d/0x1f0
btrfs_check_read_bio+0xa68/0xb70 [btrfs]
process_one_work+0xce0/0x12a0
worker_thread+0x717/0x1250
kthread+0x2e3/0x3c0
ret_from_fork+0x2d/0x70
ret_from_fork_asm+0x11/0x20
Allocated by task 20917:
kasan_save_stack+0x37/0x60
kasan_save_track+0x10/0x30
__kasan_slab_alloc+0x7d/0x80
kmem_cache_alloc_noprof+0x16e/0x3e0
mempool_alloc_noprof+0x12e/0x310
bio_alloc_bioset+0x3f0/0x7a0
btrfs_bio_alloc+0x2e/0x50 [btrfs]
submit_extent_page+0x4d1/0xdb0 [btrfs]
btrfs_do_readpage+0x8b4/0x12a0 [btrfs]
btrfs_readahead+0x29a/0x430 [btrfs]
read_pages+0x1a7/0xc60
page_cache_ra_unbounded+0x2ad/0x560
filemap_get_pages+0x629/0xa20
filemap_read+0x335/0xbf0
vfs_read+0x790/0xcb0
ksys_read+0xfd/0x1d0
do_syscall_64+0x6d/0x140
entry_SYSCALL_64_after_hwframe+0x4b/0x53
Freed by task 20917:
kasan_save_stack+0x37/0x60
kasan_save_track+0x10/0x30
kasan_save_free_info+0x37/0x50
__kasan_slab_free+0x4b/0x60
kmem_cache_free+0x214/0x5d0
bio_free+0xed/0x180
end_bbio_data_read+0x1cc/0x580 [btrfs]
btrfs_submit_chunk+0x98d/0x1880 [btrfs]
btrfs_submit_bio+0x33/0x70 [btrfs]
submit_one_bio+0xd4/0x130 [btrfs]
submit_extent_page+0x3ea/0xdb0 [btrfs]
btrfs_do_readpage+0x8b4/0x12a0 [btrfs]
btrfs_readahead+0x29a/0x430 [btrfs]
read_pages+0x1a7/0xc60
page_cache_ra_unbounded+0x2ad/0x560
filemap_get_pages+0x629/0xa20
filemap_read+0x335/0xbf0
vfs_read+0x790/0xcb0
ksys_read+0xfd/0x1d0
do_syscall_64+0x6d/0x140
entry_SYSCALL_64_after_hwframe+0x4b/0x53
[CAUSE]
Although I cannot reproduce the error, the report itself is good enough
to pin down the cause.
The call trace is the regular endio workqueue context, but the
free-by-task trace is showing that during btrfs_submit_chunk() we
already hit a critical error, and is calling btrfs_bio_end_io() to error
out. And the original endio function called bio_put() to free the whole
bio.
This means a double freeing thus causing use-after-free, e.g.:
1. Enter btrfs_submit_bio() with a read bio
The read bio length is 128K, crossing two 64K stripes.
2. The first run of btrfs_submit_chunk()
2.1 Call btrfs_map_block(), which returns 64K
2.2 Call btrfs_split_bio()
Now there are two bios, one referring to the first 64K, the other
referring to the second 64K.
2.3 The first half is submitted.
3. The second run of btrfs_submit_chunk()
3.1 Call btrfs_map_block(), which by somehow failed
Now we call btrfs_bio_end_io() to handle the error
3.2 btrfs_bio_end_io() calls the original endio function
Which is end_bbio_data_read(), and it calls bio_put() for the
original bio.
Now the original bio is freed.
4. The submitted first 64K bio finished
Now we call into btrfs_check_read_bio() and tries to advance the bio
iter.
But since the original bio (thus its iter) is already freed, we
trigger the above use-after free.
And even if the memory is not poisoned/corrupted, we will later call
the original endio function, causing a double freeing.
[FIX]
Instead of calling btrfs_bio_end_io(), call btrfs_orig_bbio_end_io(),
which has the extra check on split bios and do the proper refcounting
for cloned bios.
Furthermore there is already one extra btrfs_cleanup_bio() call, but
that is duplicated to btrfs_orig_bbio_end_io() call, so remove that
label completely.
Reported-by: David Sterba <dsterba@xxxxxxxx>
Fixes: 852eee62d31a ("btrfs: allow btrfs_submit_bio to split bios")
CC: stable@xxxxxxxxxxxxxxx # 6.6+
Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/bio.c | 26 ++++++++++++++++++--------
1 file changed, 18 insertions(+), 8 deletions(-)
--- a/fs/btrfs/bio.c
+++ b/fs/btrfs/bio.c
@@ -646,7 +646,6 @@ static bool btrfs_submit_chunk(struct bt
{
struct btrfs_inode *inode = bbio->inode;
struct btrfs_fs_info *fs_info = bbio->fs_info;
- struct btrfs_bio *orig_bbio = bbio;
struct bio *bio = &bbio->bio;
u64 logical = bio->bi_iter.bi_sector << SECTOR_SHIFT;
u64 length = bio->bi_iter.bi_size;
@@ -682,7 +681,7 @@ static bool btrfs_submit_chunk(struct bt
bbio->saved_iter = bio->bi_iter;
ret = btrfs_lookup_bio_sums(bbio);
if (ret)
- goto fail_put_bio;
+ goto fail;
}
if (btrfs_op(bio) == BTRFS_MAP_WRITE) {
@@ -704,13 +703,13 @@ static bool btrfs_submit_chunk(struct bt
ret = btrfs_bio_csum(bbio);
if (ret)
- goto fail_put_bio;
+ goto fail;
} else if (use_append ||
(btrfs_is_zoned(fs_info) && inode &&
inode->flags & BTRFS_INODE_NODATASUM)) {
ret = btrfs_alloc_dummy_sum(bbio);
if (ret)
- goto fail_put_bio;
+ goto fail;
}
}
@@ -718,12 +717,23 @@ static bool btrfs_submit_chunk(struct bt
done:
return map_length == length;
-fail_put_bio:
- if (map_length < length)
- btrfs_cleanup_bio(bbio);
fail:
btrfs_bio_counter_dec(fs_info);
- btrfs_bio_end_io(orig_bbio, ret);
+ /*
+ * We have split the original bbio, now we have to end both the current
+ * @bbio and remaining one, as the remaining one will never be submitted.
+ */
+ if (map_length < length) {
+ struct btrfs_bio *remaining = bbio->private;
+
+ ASSERT(bbio->bio.bi_pool == &btrfs_clone_bioset);
+ ASSERT(remaining);
+
+ remaining->bio.bi_status = ret;
+ btrfs_orig_bbio_end_io(remaining);
+ }
+ bbio->bio.bi_status = ret;
+ btrfs_orig_bbio_end_io(bbio);
/* Do not submit another chunk */
return true;
}
