[34-longterm 017/260] ext4: Prevent creation of files larger than RLIMIT_FSIZE using fallocate

[Paul Gortmaker]

From: Nikanth Karthikesan <knikanth@xxxxxxx>

commit 6d19c42b7cf81c39632b6d4dbc514e8449bcd346 upstream.

Currently using posix_fallocate one can bypass an RLIMIT_FSIZE limit
and create a file larger than the limit. Add a check for that.

Signed-off-by: Nikanth Karthikesan <knikanth@xxxxxxx>
Signed-off-by: Amit Arora <aarora@xxxxxxxxxx>
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
 fs/ext4/extents.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index ee611da..8a8f9f0 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3708,6 +3708,11 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
 	 */
 	credits = ext4_chunk_trans_blocks(inode, max_blocks);
 	mutex_lock(&inode->i_mutex);
+	ret = inode_newsize_ok(inode, (len + offset));
+	if (ret) {
+		mutex_unlock(&inode->i_mutex);
+		return ret;
+	}
 retry:
 	while (ret >= 0 && ret < max_blocks) {
 		block = block + ret;
-- 
1.7.3.3

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