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authorJouni Roivas <jouni.roivas@tuxera.com>2021-05-14 17:27:33 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2021-05-19 10:08:29 +0200
commitc451a6bafb5f422197d31536f82116aed132b72c (patch)
treed12258ffccac6db7a0eab41bc5df753f3d95322f
parent0b4eb172cc12dc102cd0ad013e53ee4463db9508 (diff)
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hfsplus: prevent corruption in shrinking truncate
commit c3187cf32216313fb316084efac4dab3a8459b1d upstream. I believe there are some issues introduced by commit 31651c607151 ("hfsplus: avoid deadlock on file truncation") HFS+ has extent records which always contains 8 extents. In case the first extent record in catalog file gets full, new ones are allocated from extents overflow file. In case shrinking truncate happens to middle of an extent record which locates in extents overflow file, the logic in hfsplus_file_truncate() was changed so that call to hfs_brec_remove() is not guarded any more. Right action would be just freeing the extents that exceed the new size inside extent record by calling hfsplus_free_extents(), and then check if the whole extent record should be removed. However since the guard (blk_cnt > start) is now after the call to hfs_brec_remove(), this has unfortunate effect that the last matching extent record is removed unconditionally. To reproduce this issue, create a file which has at least 10 extents, and then perform shrinking truncate into middle of the last extent record, so that the number of remaining extents is not under or divisible by 8. This causes the last extent record (8 extents) to be removed totally instead of truncating into middle of it. Thus this causes corruption, and lost data. Fix for this is simply checking if the new truncated end is below the start of this extent record, making it safe to remove the full extent record. However call to hfs_brec_remove() can't be moved to it's previous place since we're dropping ->tree_lock and it can cause a race condition and the cached info being invalidated possibly corrupting the node data. Another issue is related to this one. When entering into the block (blk_cnt > start) we are not holding the ->tree_lock. We break out from the loop not holding the lock, but hfs_find_exit() does unlock it. Not sure if it's possible for someone else to take the lock under our feet, but it can cause hard to debug errors and premature unlocking. Even if there's no real risk of it, the locking should still always be kept in balance. Thus taking the lock now just before the check. Link: https://lkml.kernel.org/r/20210429165139.3082828-1-jouni.roivas@tuxera.com Fixes: 31651c607151f ("hfsplus: avoid deadlock on file truncation") Signed-off-by: Jouni Roivas <jouni.roivas@tuxera.com> Reviewed-by: Anton Altaparmakov <anton@tuxera.com> Cc: Anatoly Trosinenko <anatoly.trosinenko@gmail.com> Cc: Viacheslav Dubeyko <slava@dubeyko.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/hfsplus/extents.c7
1 files changed, 4 insertions, 3 deletions
diff --git a/fs/hfsplus/extents.c b/fs/hfsplus/extents.c
index a930ddd15681..7054a542689f 100644
--- a/fs/hfsplus/extents.c
+++ b/fs/hfsplus/extents.c
@@ -598,13 +598,15 @@ void hfsplus_file_truncate(struct inode *inode)
res = __hfsplus_ext_cache_extent(&fd, inode, alloc_cnt);
if (res)
break;
- hfs_brec_remove(&fd);
- mutex_unlock(&fd.tree->tree_lock);
start = hip->cached_start;
+ if (blk_cnt <= start)
+ hfs_brec_remove(&fd);
+ mutex_unlock(&fd.tree->tree_lock);
hfsplus_free_extents(sb, hip->cached_extents,
alloc_cnt - start, alloc_cnt - blk_cnt);
hfsplus_dump_extent(hip->cached_extents);
+ mutex_lock(&fd.tree->tree_lock);
if (blk_cnt > start) {
hip->extent_state |= HFSPLUS_EXT_DIRTY;
break;
@@ -612,7 +614,6 @@ void hfsplus_file_truncate(struct inode *inode)
alloc_cnt = start;
hip->cached_start = hip->cached_blocks = 0;
hip->extent_state &= ~(HFSPLUS_EXT_DIRTY | HFSPLUS_EXT_NEW);
- mutex_lock(&fd.tree->tree_lock);
}
hfs_find_exit(&fd);