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btrfs: fix double put of block group with nocow 

commit 230ed39743 upstream.

While debugging a patch that I wrote I was hitting use-after-free panics
when accessing block groups on unmount.  This turned out to be because
in the nocow case if we bail out of doing the nocow for whatever reason
we need to call btrfs_dec_nocow_writers() if we called the inc.  This
puts our block group, but a few error cases does

if (nocow) {
    btrfs_dec_nocow_writers();
    goto error;
}

unfortunately, error is

error:
	if (nocow)
		btrfs_dec_nocow_writers();

so we get a double put on our block group.  Fix this by dropping the
error cases calling of btrfs_dec_nocow_writers(), as it's handled at the
error label now.

Fixes: 762bf09893 ("btrfs: improve error handling in run_delalloc_nocow")
CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5.4-rM2-2.2.x-imx-squashed
Josef Bacik 2020-07-06 09:14:12 -04:00 committed by Greg Kroah-Hartman
parent 808b2b3ea8
commit 026f830e0b
1 changed files with 1 additions and 8 deletions
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9
fs/btrfs/inode.c
View File

@ -1657,12 +1657,8 @@ out_check:
ret = fallback_to_cow(inode, locked_page, cow_start,
found_key.offset - 1,
page_started, nr_written);
if (ret) {
if (nocow)
btrfs_dec_nocow_writers(fs_info,
disk_bytenr);
if (ret)
goto error;
}
cow_start = (u64)-1;
}
@ -1678,9 +1674,6 @@ out_check:
ram_bytes, BTRFS_COMPRESS_NONE,
BTRFS_ORDERED_PREALLOC);
if (IS_ERR(em)) {
if (nocow)
btrfs_dec_nocow_writers(fs_info,
disk_bytenr);
ret = PTR_ERR(em);
goto error;
}