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btrfs: don't propagate EXTENT_FLAG_LOGGING to split extent maps

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When btrfs_drop_extent_map_range() splits an extent map, the new split
maps inherit the original map's flags through a local 'flags' variable.
Commit f86f7a75e2 ("btrfs: use the flags of an extent map to identify
the compression type") changed the EXTENT_FLAG_LOGGING clearing to
operate on em->flags instead of that local 'flags' copy, so a split of
an extent map that is currently being logged wrongly inherits
EXTENT_FLAG_LOGGING.

The flag is then never cleared on the split, and when it is freed while
still on the inode's modified_extents list (for example by the extent
map shrinker) it trips the WARN_ON(!list_empty(&em->list)) in
btrfs_free_extent_map() and leads to a use-after-free.

Clear EXTENT_FLAG_LOGGING from the local 'flags' copy used for the
splits and only clear EXTENT_FLAG_PINNED from em->flags, restoring the
behaviour prior to f86f7a75e2.

CC: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/all/20260629-btrfs-skip-logging-v1-1-4e3a28c1acaf@kernel.org/
Fixes: f86f7a75e2 ("btrfs: use the flags of an extent map to identify the compression type")
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Leo Martins <loemra.dev@gmail.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Leo Martins
2026-06-30 12:58:05 -07:00
committed by David Sterba
parent 8b5a09ceb6
commit 5eff4d5b17
1 changed files with 2 additions and 2 deletions
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4
fs/btrfs/extent_map.c
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@@ -866,13 +866,13 @@ void btrfs_drop_extent_map_range(struct btrfs_inode *inode, u64 start, u64 end,
goto next;
}
flags = em->flags;
/*
* In case we split the extent map, we want to preserve the
* EXTENT_FLAG_LOGGING flag on our extent map, but we don't want
* it on the new extent maps.
*/
em->flags &= ~(EXTENT_FLAG_PINNED | EXTENT_FLAG_LOGGING);
flags = em->flags & ~EXTENT_FLAG_LOGGING;
em->flags &= ~EXTENT_FLAG_PINNED;
modified = !list_empty(&em->list);
/*