[PATCH 0/2] smb/client: fix emulated insert range handling

[PATCH 0/2] smb/client: fix emulated insert range handling

[Huiwen He]

From: Huiwen He <hehuiwen@kylinos.cn>

This series fixes two issues in the SMB3 FALLOC_FL_INSERT_RANGE
emulation.

Patch 1 fixes missing new EOF validation, which allowed RLIMIT_FSIZE to
be bypassed.

Patch 2 preserves hole semantics for inserted ranges, fixing xfstests
generic/064 against Samba and ksmbd.

In my Windows Server testing, aligned 64 KiB and 128 KiB insert ranges
were reported as holes, but generic/064 still fails because it uses
4 KiB inserts. Azure Files may not pass the test because it does not
support sparse files.

Thanks,
Huiwen

Huiwen He (2):
  smb/client: validate new EOF for insert range
  smb/client: mark file sparse before emulating insert range

 fs/smb/client/smb2ops.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

-- 
2.43.0

[PATCH 1/2] smb/client: validate new EOF for insert range

[Huiwen He]

From: Huiwen He <hehuiwen@kylinos.cn>

smb3_insert_range() does not check if the new file size
(i_size + len) is valid. This allows FALLOC_FL_INSERT_RANGE to bypass
RLIMIT_FSIZE, exceed s_maxbytes, or produce a size outside the loff_t
range.

Use check_add_overflow() to calculate the new EOF. Validate it with
inode_newsize_ok() before modifying the file.

Reproducer, using a file on a CIFS mount:

	bash -c '
		FILE=/mnt/cifs/repro

		trap "" SIGXFSZ
		ulimit -f 3072		# RLIMIT_FSIZE = 3 MiB

		# A regular write is stopped at 3 MiB.
		dd if=/dev/zero of="$FILE" bs=1M count=4 status=none
		stat -c "size after write: %s" "$FILE"

		# Insert 2 MiB into a 2 MiB file.
		truncate -s 2M "$FILE"
		fallocate -i -o 0 -l 2M "$FILE"
		stat -c "size after insert: %s" "$FILE"
	'

Before this change, the regular write stops at the 3 MiB limit, but
insert range grows the file to 4 MiB:

	dd: error writing '/mnt/cifs/repro': File too large
	size after write: 3145728
	size after insert: 4194304

After this change, insert range also fails at the limit and leaves the
2 MiB file unchanged:

	dd: error writing '/mnt/cifs/repro': File too large
	size after write: 3145728
	fallocate: fallocate failed: File too large
	size after insert: 2097152

Fixes: 7fe6fe95b936 ("cifs: add FALLOC_FL_INSERT_RANGE support")
Signed-off-by: Huiwen He <hehuiwen@kylinos.cn>
Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
---
 fs/smb/client/smb2ops.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index 192649fec25d..bc7dda6d825a 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -3985,7 +3985,8 @@ static long smb3_insert_range(struct file *file, struct cifs_tcon *tcon,
 	struct cifsFileInfo *cfile = file->private_data;
 	struct inode *inode = file_inode(file);
 	struct cifsInodeInfo *cifsi = CIFS_I(inode);
-	__u64 count, old_eof, new_eof;
+	u64 count;
+	loff_t old_eof, new_eof;
 
 	xid = get_xid();
 
@@ -3995,8 +3996,15 @@ static long smb3_insert_range(struct file *file, struct cifs_tcon *tcon,
 		goto out;
 	}
 
+	if (check_add_overflow(old_eof, len, &new_eof)) {
+		rc = -EFBIG;
+		goto out;
+	}
+	rc = inode_newsize_ok(inode, new_eof);
+	if (rc)
+		goto out;
+
 	count = old_eof - off;
-	new_eof = old_eof + len;
 
 	filemap_invalidate_lock(inode->i_mapping);
 	rc = filemap_write_and_wait_range(inode->i_mapping, off, new_eof - 1);
-- 
2.43.0

[PATCH 2/2] smb/client: mark file sparse before emulating insert range

[Huiwen He]

From: Huiwen He <hehuiwen@kylinos.cn>

The SMB client emulates FALLOC_FL_INSERT_RANGE with SET_EOF, COPYCHUNK
and SET_ZERO_DATA.

SET_ZERO_DATA creates a hole only when the file is sparse. On a
non-sparse file, it clears the inserted range but leaves its blocks
allocated, causing the extent count check in xfstests generic/064 to
fail.

Try to mark the file sparse before starting the emulation. As with
existing file extension paths, ignore SET_SPARSE errors and continue
with the existing zero-filled behavior.

Tested with xfstests generic/064 against Samba and ksmbd.

Fixes: 7fe6fe95b936 ("cifs: add FALLOC_FL_INSERT_RANGE support")
Signed-off-by: Huiwen He <hehuiwen@kylinos.cn>
Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
---
 fs/smb/client/smb2ops.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index bc7dda6d825a..430b6a1a2d92 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -4006,6 +4006,12 @@ static long smb3_insert_range(struct file *file, struct cifs_tcon *tcon,
 
 	count = old_eof - off;
 
+	/*
+	 * SET_ZERO_DATA creates a hole only in a sparse file. Try to mark the file
+	 * sparse, but continue the emulation regardless of the result.
+	 */
+	smb2_set_sparse(xid, tcon, cfile, inode, true);
+
 	filemap_invalidate_lock(inode->i_mapping);
 	rc = filemap_write_and_wait_range(inode->i_mapping, off, new_eof - 1);
 	if (rc < 0)
-- 
2.43.0