FAILED: patch "[PATCH] ksmbd: fix named stream write and EOF handling" failed to apply to 6.12-stable tree

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 02165c8d402392278a5cd2cf97645ed73a7ad4a1
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026110332-browsing-plentiful-ef07@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 02165c8d402392278a5cd2cf97645ed73a7ad4a1 Mon Sep 17 00:00:00 2001
From: DaeMyung Kang <[email protected]>
Date: Wed, 7 Oct 2026 22:13:51 +0900
Subject: [PATCH] ksmbd: fix named stream write and EOF handling

An SMB WRITE to an existing named stream can silently discard data after its written range. ksmbd stores streams as xattr values, but the write path passes offset + count as the length of the replacement xattr even when the old stream is longer. Writing 26 bytes at offset 0 to a 60-byte stream reports 26 bytes written while discarding the remaining 34 bytes.

Keep the existing xattr length when an in-place write ends before EOF. Reject writes that cross XATTR_SIZE_MAX rather than storing only the portion that fits while reporting the full requested count.

Commit 4ea0bb8aaedf ("ksmbd: handle set/get info file for streamed file") intentionally skipped ordinary inode truncation for stream handles: an EOF SetInfo on an ADS had truncated the base file. That fixed the base file corruption but left stream EOF changes reporting success without resizing the stream. Handle these requests by resizing only the stream xattr; the base file size remains untouched. Zero-fill stream extensions. This is needed alongside the write fix: a short write's accidental truncation previously masked an ignored explicit EOF change. The stream resize helper returns xattr errors directly rather than using the base-file truncate path's EBADF conversion.

index a400f9912896..0fb146b612f0 100644
@@ -8578,6 +8578,8 @@ static int set_end_of_file_info(struct ksmbd_work *work, struct ksmbd_file *fp,
 
 	newsize = le64_to_cpu(file_eof_info->EndOfFile);
 	inode = file_inode(fp->filp);
+	if (ksmbd_stream_fd(fp))
+		return ksmbd_vfs_stream_truncate(fp, newsize);
 
 	/*
 	 * If FILE_END_OF_FILE_INFORMATION of set_info_file is called

@@ -8586,8 +8588,7 @@ static int set_end_of_file_info(struct ksmbd_work *work, struct ksmbd_file *fp,
 	 * truncate of some filesystem like FAT32 fill zero data in
 	 * truncated range.
 	 */
-	if (inode->i_sb->s_magic != MSDOS_SUPER_MAGIC &&
-	    ksmbd_stream_fd(fp) == false) {
+	if (inode->i_sb->s_magic != MSDOS_SUPER_MAGIC) {
 		ksmbd_debug(SMB, "truncated to newsize %lld\n", newsize);
 		rc = ksmbd_vfs_truncate(work, fp, newsize);
 		if (rc) {

index 216c76291fc1..7e545d13a3ff 100644
@@ -83,6 +83,7 @@ int ksmbd_vfs_read(struct ksmbd_work *work, struct ksmbd_file *fp, size_t count,
 int ksmbd_vfs_write(struct ksmbd_work *work, struct ksmbd_file *fp,
 		    char *buf, size_t count, loff_t *pos, bool sync,
 		    ssize_t *written);
+int ksmbd_vfs_stream_truncate(struct ksmbd_file *fp, loff_t newsize);
 int ksmbd_vfs_fsync(struct ksmbd_work *work, u64 fid, u64 p_id);
 int ksmbd_vfs_remove_file(struct ksmbd_work *work, const struct path *path);
 int ksmbd_vfs_link(struct ksmbd_work *work,

From: DaeMyung Kang <[email protected]>

[ Upstream commit 02165c8d402392278a5cd2cf97645ed73a7ad4a1 ]

An SMB WRITE to an existing named stream can silently discard data after its written range. ksmbd stores streams as xattr values, but the write path passes offset + count as the length of the replacement xattr even when the old stream is longer. Writing 26 bytes at offset 0 to a 60-byte stream reports 26 bytes written while discarding the remaining 34 bytes.

Keep the existing xattr length when an in-place write ends before EOF. Reject writes that cross XATTR_SIZE_MAX rather than storing only the portion that fits while reporting the full requested count.

Commit 4ea0bb8aaedf ("ksmbd: handle set/get info file for streamed file") intentionally skipped ordinary inode truncation for stream handles: an EOF SetInfo on an ADS had truncated the base file. That fixed the base file corruption but left stream EOF changes reporting success without resizing the stream. Handle these requests by resizing only the stream xattr; the base file size remains untouched. Zero-fill stream extensions. This is needed alongside the write fix: a short write's accidental truncation previously masked an ignored explicit EOF change. The stream resize helper returns xattr errors directly rather than using the base-file truncate path's EBADF conversion.

---
 fs/smb/server/smb2pdu.c |  2 ++
 fs/smb/server/vfs.c     | 72 ++++++++++++++++++++++++++++++++++++-----
 fs/smb/server/vfs.h     |  1 +
 3 files changed, 67 insertions(+), 8 deletions(-)

index 5f752434be3cf..0ebf9644e5367 100644
@@ -6525,6 +6525,8 @@ static int set_end_of_file_info(struct ksmbd_work *work, struct ksmbd_file *fp,
 
 	newsize = le64_to_cpu(file_eof_info->EndOfFile);
 	inode = file_inode(fp->filp);
+	if (ksmbd_stream_fd(fp))
+		return ksmbd_vfs_stream_truncate(fp, newsize);
 
 	/*
 	 * If FILE_END_OF_FILE_INFORMATION of set_info_file is called

index 06903024a2d88..526c0541ec691 100644
@@ -82,6 +82,7 @@ int ksmbd_vfs_read(struct ksmbd_work *work, struct ksmbd_file *fp, size_t count,
 int ksmbd_vfs_write(struct ksmbd_work *work, struct ksmbd_file *fp,
 		    char *buf, size_t count, loff_t *pos, bool sync,
 		    ssize_t *written);
+int ksmbd_vfs_stream_truncate(struct ksmbd_file *fp, loff_t newsize);
 int ksmbd_vfs_fsync(struct ksmbd_work *work, u64 fid, u64 p_id);
 int ksmbd_vfs_remove_file(struct ksmbd_work *work, const struct path *path);
 int ksmbd_vfs_link(struct ksmbd_work *work,

2.53.0