From: Eric Biggers <ebiggers@xxxxxxxxxx>
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 doing an unsigned comparison 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@xxxxxxxxxxxxxxx> # v4.1+
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
fs/xfs/xfs_file.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 299aee4b7b0b..56a820efeb2a 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -786,8 +786,11 @@ xfs_file_fallocate(
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 ((u64)new_size > inode->i_sb->s_maxbytes) {
error = -EFBIG;
goto out_unlock;
}
--
2.17.0.484.g0c8726318c-goog
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