diff options
| author | David Sterba <dsterba@suse.com> | 2020-01-08 15:29:53 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-02-28 16:36:05 +0100 |
| commit | 76d4e6aeac0b7cb830f72780e89b96ba3052118f (patch) | |
| tree | 47047d601a277add085f36555f2134bf089ccf56 /fs | |
| parent | ad915b3d80144a437dd3c08491a72e0bb4154a2a (diff) | |
btrfs: safely advance counter when looking up bio csums
[ Upstream commit 4babad10198fa73fe73239d02c2e99e3333f5f5c ]
Dan's smatch tool reports
fs/btrfs/file-item.c:295 btrfs_lookup_bio_sums()
warn: should this be 'count == -1'
which points to the while (count--) loop. With count == 0 the check
itself could decrement it to -1. There's a WARN_ON a few lines below
that has never been seen in practice though.
It turns out that the value of page_bytes_left matches the count (by
sectorsize multiples). The loop never reaches the state where count
would go to -1, because page_bytes_left == 0 is found first and this
breaks out.
For clarity, use only plain check on count (and only for positive
value), decrement safely inside the loop. Any other discrepancy after
the whole bio list processing should be reported by the exising
WARN_ON_ONCE as well.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/btrfs/file-item.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c index 702b3606ad0e..717d82d51bb1 100644 --- a/fs/btrfs/file-item.c +++ b/fs/btrfs/file-item.c @@ -288,7 +288,8 @@ found: csum += count * csum_size; nblocks -= count; next: - while (count--) { + while (count > 0) { + count--; disk_bytenr += fs_info->sectorsize; offset += fs_info->sectorsize; page_bytes_left -= fs_info->sectorsize; |