Commit f18b2b83 authored Oct 02, 2018 by Theodore Ts'o

ext4: fix argument checking in EXT4_IOC_MOVE_EXT



If the starting block number of either the source or destination file
exceeds the EOF, EXT4_IOC_MOVE_EXT should return EINVAL.

Also fixed the helper function mext_check_coverage() so that if the
logical block is beyond EOF, make it return immediately, instead of
looping until the block number wraps all the away around.  This takes
long enough that if there are multiple threads trying to do pound on
an the same inode doing non-sensical things, it can end up triggering
the kernel's soft lockup detector.

Reported-by:  <syzbot+c61979f6f2cba5cb3c06@syzkaller.appspotmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org

parent f456767d

fs/ext4/move_extent.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -516,9 +516,13 @@ mext_check_arguments(struct inode *orig_inode,
		orig_inode->i_ino, donor_inode->i_ino);
		return -EINVAL;
		}
		if (orig_eof < orig_start + *len - 1)
		if (orig_eof <= orig_start)
		*len = 0;
		else if (orig_eof < orig_start + *len - 1)
		*len = orig_eof - orig_start;
		if (donor_eof < donor_start + *len - 1)
		if (donor_eof <= donor_start)
		*len = 0;
		else if (donor_eof < donor_start + *len - 1)
		*len = donor_eof - donor_start;
		if (!*len) {
		ext4_debug("ext4 move extent: len should not be 0 "

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