[PATCH 6.12.y 1/2] smb: client: correctly handle ErrorContextData as a flexible array

[PATCH 6.12.y 1/2] smb: client: correctly handle ErrorContextData as a flexible array

[Alva Lan]

From: Liang Jie <liangjie@lixiang.com>

[ Upstream commit 215b7f9ecb8d7c14d56febdcdd246f3579c32aba ]

The `smb2_symlink_err_rsp` structure was previously defined with
`ErrorContextData` as a single `__u8` byte. However, the `ErrorContextData`
field is intended to be a variable-length array based on `ErrorDataLength`.
This mismatch leads to incorrect pointer arithmetic and potential memory
access issues when processing error contexts.

Updates the `ErrorContextData` field to be a flexible array
(`__u8 ErrorContextData[]`). Additionally, it modifies the corresponding
casts in the `symlink_data()` function to properly handle the flexible
array, ensuring correct memory calculations and data handling.

These changes improve the robustness of SMB2 symlink error processing.

Signed-off-by: Liang Jie <liangjie@lixiang.com>
Suggested-by: Tom Talpey <tom@talpey.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Alva Lan <alvalan9@foxmail.com>
---
 fs/smb/client/smb2file.c | 4 ++--
 fs/smb/client/smb2pdu.h  | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/smb/client/smb2file.c b/fs/smb/client/smb2file.c
index b7ab18d4bedc..35d2933982d3 100644
--- a/fs/smb/client/smb2file.c
+++ b/fs/smb/client/smb2file.c
@@ -42,14 +42,14 @@ static struct smb2_symlink_err_rsp *symlink_data(const struct kvec *iov)
 		end = (struct smb2_error_context_rsp *)((u8 *)err + iov->iov_len);
 		do {
 			if (le32_to_cpu(p->ErrorId) == SMB2_ERROR_ID_DEFAULT) {
-				sym = (struct smb2_symlink_err_rsp *)&p->ErrorContextData;
+				sym = (struct smb2_symlink_err_rsp *)p->ErrorContextData;
 				break;
 			}
 			cifs_dbg(FYI, "%s: skipping unhandled error context: 0x%x\n",
 				 __func__, le32_to_cpu(p->ErrorId));
 
 			len = ALIGN(le32_to_cpu(p->ErrorDataLength), 8);
-			p = (struct smb2_error_context_rsp *)((u8 *)&p->ErrorContextData + len);
+			p = (struct smb2_error_context_rsp *)(p->ErrorContextData + len);
 		} while (p < end);
 	} else if (le32_to_cpu(err->ByteCount) >= sizeof(*sym) &&
 		   iov->iov_len >= SMB2_SYMLINK_STRUCT_SIZE) {
diff --git a/fs/smb/client/smb2pdu.h b/fs/smb/client/smb2pdu.h
index 076d9e83e1a0..3c09a58dfd07 100644
--- a/fs/smb/client/smb2pdu.h
+++ b/fs/smb/client/smb2pdu.h
@@ -79,7 +79,7 @@ struct smb2_symlink_err_rsp {
 struct smb2_error_context_rsp {
 	__le32 ErrorDataLength;
 	__le32 ErrorId;
-	__u8  ErrorContextData; /* ErrorDataLength long array */
+	__u8  ErrorContextData[] __counted_by_le(ErrorDataLength);
 } __packed;
 
 /* ErrorId values */
-- 
2.43.0

Re: [PATCH 6.12.y 1/2] smb: client: correctly handle ErrorContextData as a flexible array

[Sasha Levin]

On Sun, May 17, 2026, Alva Lan wrote:
> From: Liang Jie <liangjie@lixiang.com>
>
> [ Upstream commit 215b7f9ecb8d7c14d56febdcdd246f3579c32aba ]

Queued for 6.12, thanks.

--
Thanks,
Sasha