From 01261a6fa48b62f5ead8e88aaca1e27cb9ab9032 Mon Sep 17 00:00:00 2001 From: Huiwen He Date: Fri, 28 Aug 2026 15:19:34 +0800 Subject: [PATCH] smb/client: fix stale page cache in insert/collapse range smb3_insert_range() and smb3_collapse_range() use truncate_pagecache_range() to invalidate the affected page cache. However, if off or old_eof is not page-aligned, the boundary pages are only partially zeroed and remain uptodate. As a result, the client may return stale data after a successful insert/collapse range operation. For example, with 4K pages: page 0 page 1 page 2 0------4K 4K------8K 8K------12K ^ ^ off=2K old_eof=10K Page 1 is removed from the page cache, while the boundary pages are only partially zeroed. After COPYCHUNK moves the data on the server, these cached pages may still return stale data. This can be reproduced on a CIFS mount: bash -c ' FILE=/mnt/scratch/repro # Use a 6 KiB file so EOF is not page-aligned. dd if=/dev/urandom of=/tmp/src bs=1K count=6 status=none # Expected: a 4 KiB hole followed by the original data. rm -f /tmp/expected truncate -s 4K /tmp/expected cat /tmp/src >> /tmp/expected cp /tmp/src "$FILE" # Prime the page cache before moving data on the server. cat "$FILE" > /dev/null fallocate --insert-range -o 0 -l 4K "$FILE" if cmp -s /tmp/expected "$FILE"; then echo "readback: OK" else echo "readback: STALE DATA" fi ' Fix this by writing back dirty data and discarding the page cache from the start of the page containing off to EOF before moving data on the server. Fixes: 9c8b7a293f50 ("smb3: fix temporary data corruption in insert range") Fixes: fa30a81f255a ("smb3: fix temporary data corruption in collapse range") Signed-off-by: Huiwen He Reviewed-by: ChenXiaoSong Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara --- fs/smb/client/smb2ops.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c index 1d476a8af863..cd5e31b578f9 100644 --- a/fs/smb/client/smb2ops.c +++ b/fs/smb/client/smb2ops.c @@ -4026,15 +4026,22 @@ static long smb3_collapse_range(struct file *file, struct cifs_tcon *tcon, } filemap_invalidate_lock(inode->i_mapping); - rc = filemap_write_and_wait_range(inode->i_mapping, off, old_eof - 1); + rc = filemap_write_and_wait_range(inode->i_mapping, + round_down(off, PAGE_SIZE), + old_eof - 1); if (rc < 0) goto out_2; - truncate_pagecache_range(inode, off, old_eof); + netfs_wait_for_outstanding_io(inode); + /* + * Invalidate cached folios from the page containing off to EOF before + * moving data on the server, so subsequent reads do not see stale data. + */ + truncate_pagecache_range(inode, round_down(off, PAGE_SIZE), -1); + spin_lock(&inode->i_lock); netfs_write_zero_point(inode, old_eof); spin_unlock(&inode->i_lock); - netfs_wait_for_outstanding_io(inode); rc = __smb2_copychunk_range(xid, cfile, cfile, off + len, old_eof - off - len, off); @@ -4094,11 +4101,17 @@ static long smb3_insert_range(struct file *file, struct cifs_tcon *tcon, goto out; filemap_invalidate_lock(inode->i_mapping); - rc = filemap_write_and_wait_range(inode->i_mapping, off, new_eof - 1); + rc = filemap_write_and_wait_range(inode->i_mapping, + round_down(off, PAGE_SIZE), + old_eof - 1); if (rc < 0) goto out_2; - truncate_pagecache_range(inode, off, old_eof); netfs_wait_for_outstanding_io(inode); + /* + * Invalidate cached folios from the page containing off to EOF before + * moving data on the server, so subsequent reads do not see stale data. + */ + truncate_pagecache_range(inode, round_down(off, PAGE_SIZE), -1); rc = SMB2_set_eof(xid, tcon, cfile->fid.persistent_fid, cfile->fid.volatile_fid, cfile->pid, new_eof);