lkml.org 
[lkml]   [2018]   [May]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.14 19/43] xfs: prevent creating negative-sized file via INSERT_RANGE
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Darrick J. Wong <darrick.wong@oracle.com>

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>

---
fs/xfs/xfs_file.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)

--- 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;
}

\
 
 \ /
  Last update: 2018-05-08 10:43    [W:0.123 / U:1.128 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site