diff options
author | Qu Wenruo <wqu@suse.com> | 2021-03-15 13:39:14 +0800 |
---|---|---|
committer | David Sterba <dsterba@suse.com> | 2021-03-16 11:06:18 +0100 |
commit | d9bb77d51e668a1a6d4530c1ea471574d0ce465f (patch) | |
tree | ce0fd3c73a375a017950e9f3436b06242154fd41 /fs | |
parent | e3d3b4157610164b0ec43d968b0dfedfe7c68992 (diff) | |
download | linux-d9bb77d51e668a1a6d4530c1ea471574d0ce465f.tar.bz2 |
btrfs: subpage: fix wild pointer access during metadata read failure
[BUG]
When running fstests for btrfs subpage read-write test, it has a very
high chance to crash at generic/475 with the following stack:
BTRFS warning (device dm-8): direct IO failed ino 510 rw 1,34817 sector 0xcdf0 len 94208 err no 10
Unable to handle kernel paging request at virtual address ffff80001157e7c0
CPU: 2 PID: 687125 Comm: kworker/u12:4 Tainted: G WC 5.12.0-rc2-custom+ #5
Hardware name: Khadas VIM3 (DT)
Workqueue: btrfs-endio-meta btrfs_work_helper [btrfs]
pc : queued_spin_lock_slowpath+0x1a0/0x390
lr : do_raw_spin_lock+0xc4/0x11c
Call trace:
queued_spin_lock_slowpath+0x1a0/0x390
_raw_spin_lock+0x68/0x84
btree_readahead_hook+0x38/0xc0 [btrfs]
end_bio_extent_readpage+0x504/0x5f4 [btrfs]
bio_endio+0x170/0x1a4
end_workqueue_fn+0x3c/0x60 [btrfs]
btrfs_work_helper+0x1b0/0x1b4 [btrfs]
process_one_work+0x22c/0x430
worker_thread+0x70/0x3a0
kthread+0x13c/0x140
ret_from_fork+0x10/0x30
Code: 910020e0 8b0200c2 f861d884 aa0203e1 (f8246827)
[CAUSE]
In end_bio_extent_readpage(), if we hit an error during read, we will
handle the error differently for data and metadata.
For data we queue a repair, while for metadata, we record the error and
let the caller choose what to do.
But the code is still using page->private to grab extent buffer, which
no longer points to extent buffer for subpage metadata pages.
Thus this wild pointer access leads to above crash.
[FIX]
Introduce a helper, find_extent_buffer_readpage(), to grab extent
buffer.
The difference against find_extent_buffer_nospinlock() is:
- Also handles regular sectorsize == PAGE_SIZE case
- No extent buffer refs increase/decrease
As extent buffer under IO must have non-zero refs, so this is safe
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/btrfs/extent_io.c | 31 |
1 files changed, 30 insertions, 1 deletions
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index f3d7be975c3a..0d00a9cd123a 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -2886,6 +2886,35 @@ static void end_page_read(struct page *page, bool uptodate, u64 start, u32 len) } /* + * Find extent buffer for a givne bytenr. + * + * This is for end_bio_extent_readpage(), thus we can't do any unsafe locking + * in endio context. + */ +static struct extent_buffer *find_extent_buffer_readpage( + struct btrfs_fs_info *fs_info, struct page *page, u64 bytenr) +{ + struct extent_buffer *eb; + + /* + * For regular sectorsize, we can use page->private to grab extent + * buffer + */ + if (fs_info->sectorsize == PAGE_SIZE) { + ASSERT(PagePrivate(page) && page->private); + return (struct extent_buffer *)page->private; + } + + /* For subpage case, we need to lookup buffer radix tree */ + rcu_read_lock(); + eb = radix_tree_lookup(&fs_info->buffer_radix, + bytenr >> fs_info->sectorsize_bits); + rcu_read_unlock(); + ASSERT(eb); + return eb; +} + +/* * after a readpage IO is done, we need to: * clear the uptodate bits on error * set the uptodate bits if things worked @@ -2996,7 +3025,7 @@ static void end_bio_extent_readpage(struct bio *bio) } else { struct extent_buffer *eb; - eb = (struct extent_buffer *)page->private; + eb = find_extent_buffer_readpage(fs_info, page, start); set_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags); eb->read_mirror = mirror; atomic_dec(&eb->io_pages); |