4.16-stable review patch. If anyone has any objections, please let me know.
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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 @@ -812,22 +812,26 @@ 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; }