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authorDarrick J. Wong <darrick.wong@oracle.com>2018-04-16 23:07:45 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-05-09 09:51:52 +0200
commitbd9ca962eeb05767efed7c2dd62d201a54a9d727 (patch)
tree4ef94cdbc4265568dbd97fecd40dd7442cd52e5a
parentb68c7af0b2e7d3675c67e977b200466e26142a7e (diff)
xfs: prevent creating negative-sized file via INSERT_RANGE
commit 7d83fb14258b9961920cd86f0b921caaeb3ebe85 upstream. 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: a904b1ca5751 ("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: Eric Biggers <ebiggers@google.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> [darrick: fix signed integer addition overflow too] Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/xfs/xfs_file.c14
1 files changed, 9 insertions, 5 deletions
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 6526ef0e2a23..fa68e81e9671 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -811,22 +811,26 @@ 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;
}