Commit 7d83fb14 authored by Darrick J. Wong's avatar Darrick J. Wong

xfs: prevent creating negative-sized file via INSERT_RANGE


During the "insert range" fallocate operation, i_size grows by the
specified 'len' bytes.  XFS verifies that i_size + len < s_maxbytes, as
it should.  But this comparison is done using the signed 'loff_t', and
'i_size + len' can wrap around to a negative value, causing the check to
incorrectly pass, resulting in an inode with "negative" i_size.  This is
possible on 64-bit platforms, where XFS sets s_maxbytes = LLONG_MAX.
ext4 and f2fs don't run into this because they set a smaller s_maxbytes.

Fix it by using subtraction instead.

Reproducer:
    xfs_io -f file -c "truncate $(((1<<63)-1))" -c "finsert 0 4096"

Fixes: a904b1ca ("xfs: Add support FALLOC_FL_INSERT_RANGE for fallocate")
Cc: <stable@vger.kernel.org> # v4.1+
Originally-From: Eric Biggers <ebiggers@google.com>
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
[darrick: fix signed integer addition overflow too]
Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
parent 2c4306f7
......@@ -778,22 +778,26 @@ xfs_file_fallocate(
if (error)
goto out_unlock;
} else if (mode & FALLOC_FL_INSERT_RANGE) {
unsigned int blksize_mask = i_blocksize(inode) - 1;
unsigned int blksize_mask = i_blocksize(inode) - 1;
loff_t isize = i_size_read(inode);
new_size = i_size_read(inode) + len;
if (offset & blksize_mask || len & blksize_mask) {
error = -EINVAL;
goto out_unlock;
}
/* check the new inode size does not wrap through zero */
if (new_size > inode->i_sb->s_maxbytes) {
/*
* New inode size must not exceed ->s_maxbytes, accounting for
* possible signed overflow.
*/
if (inode->i_sb->s_maxbytes - isize < len) {
error = -EFBIG;
goto out_unlock;
}
new_size = isize + len;
/* Offset should be less than i_size */
if (offset >= i_size_read(inode)) {
if (offset >= isize) {
error = -EINVAL;
goto out_unlock;
}
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment