ext4: work around deleting a file with i_nlink == 0 safely
BugLink: https://bugs.launchpad.net/bugs/1858462 [ Upstream commit c7df4a1e ] If the file system is corrupted such that a file's i_links_count is too small, then it's possible that when unlinking that file, i_nlink will already be zero. Previously we were working around this kind of corruption by forcing i_nlink to one; but we were doing this before trying to delete the directory entry --- and if the file system is corrupted enough that ext4_delete_entry() fails, then we exit with i_nlink elevated, and this causes the orphan inode list handling to be FUBAR'ed, such that when we unmount the file system, the orphan inode list can get corrupted. A better way to fix this is to simply skip trying to call drop_nlink() if i_nlink is already zero, thus moving the check to the place where it makes the most sense. https://bugzilla.kernel.org/show_bug.cgi?id=205433 Link: https://lore.kernel.org/r/20191112032903.8828-1-tytso@mit.eduSigned-off-by: Theodore Ts'o <tytso@mit.edu> Cc: stable@kernel.org Reviewed-by: Andreas Dilger <adilger@dilger.ca> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com> Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
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