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Message-Id: <20250505223922.2682012-7-sashal@kernel.org>
Date: Mon, 5 May 2025 18:31:23 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
stable@...r.kernel.org
Cc: Wang Zhaolong <wangzhaolong1@...wei.com>,
Steve French <stfrench@...rosoft.com>,
Sasha Levin <sashal@...nel.org>,
sfrench@...ba.org,
linkinjeon@...nel.org,
linux-cifs@...r.kernel.org,
samba-technical@...ts.samba.org
Subject: [PATCH AUTOSEL 6.12 007/486] smb: client: Store original IO parameters and prevent zero IO sizes
From: Wang Zhaolong <wangzhaolong1@...wei.com>
[ Upstream commit 287906b20035a04a234d1a3c64f760a5678387be ]
During mount option processing and negotiation with the server, the
original user-specified rsize/wsize values were being modified directly.
This makes it impossible to recover these values after a connection
reset, leading to potential degraded performance after reconnection.
The other problem is that When negotiating read and write sizes, there are
cases where the negotiated values might calculate to zero, especially
during reconnection when server->max_read or server->max_write might be
reset. In general, these values come from the negotiation response.
According to MS-SMB2 specification, these values should be at least 65536
bytes.
This patch improves IO parameter handling:
1. Adds vol_rsize and vol_wsize fields to store the original user-specified
values separately from the negotiated values
2. Uses got_rsize/got_wsize flags to determine if values were
user-specified rather than checking for non-zero values, which is more
reliable
3. Adds a prevent_zero_iosize() helper function to ensure IO sizes are
never negotiated down to zero, which could happen in edge cases like
when server->max_read/write is zero
The changes make the CIFS client more resilient to unusual server
responses and reconnection scenarios, preventing potential failures
when IO sizes are calculated to be zero.
Signed-off-by: Wang Zhaolong <wangzhaolong1@...wei.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
fs/smb/client/fs_context.c | 2 ++
fs/smb/client/fs_context.h | 3 +++
fs/smb/client/smb1ops.c | 6 +++---
fs/smb/client/smb2ops.c | 27 +++++++++++++++++++--------
fs/smb/common/smb2pdu.h | 3 +++
5 files changed, 30 insertions(+), 11 deletions(-)
diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
index 1f1f4586673a7..66d872d63f839 100644
--- a/fs/smb/client/fs_context.c
+++ b/fs/smb/client/fs_context.c
@@ -1237,6 +1237,7 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
case Opt_rsize:
ctx->rsize = result.uint_32;
ctx->got_rsize = true;
+ ctx->vol_rsize = ctx->rsize;
break;
case Opt_wsize:
ctx->wsize = result.uint_32;
@@ -1252,6 +1253,7 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
ctx->wsize, PAGE_SIZE);
}
}
+ ctx->vol_wsize = ctx->wsize;
break;
case Opt_acregmax:
if (result.uint_32 > CIFS_MAX_ACTIMEO / HZ) {
diff --git a/fs/smb/client/fs_context.h b/fs/smb/client/fs_context.h
index c8c8b4451b3bc..90ebff5d0199d 100644
--- a/fs/smb/client/fs_context.h
+++ b/fs/smb/client/fs_context.h
@@ -253,6 +253,9 @@ struct smb3_fs_context {
bool use_client_guid:1;
/* reuse existing guid for multichannel */
u8 client_guid[SMB2_CLIENT_GUID_SIZE];
+ /* User-specified original r/wsize value */
+ unsigned int vol_rsize;
+ unsigned int vol_wsize;
unsigned int bsize;
unsigned int rasize;
unsigned int rsize;
diff --git a/fs/smb/client/smb1ops.c b/fs/smb/client/smb1ops.c
index a2dbebd13720b..71fe5aa52630d 100644
--- a/fs/smb/client/smb1ops.c
+++ b/fs/smb/client/smb1ops.c
@@ -437,8 +437,8 @@ cifs_negotiate_wsize(struct cifs_tcon *tcon, struct smb3_fs_context *ctx)
unsigned int wsize;
/* start with specified wsize, or default */
- if (ctx->wsize)
- wsize = ctx->wsize;
+ if (ctx->got_wsize)
+ wsize = ctx->vol_wsize;
else if (tcon->unix_ext && (unix_cap & CIFS_UNIX_LARGE_WRITE_CAP))
wsize = CIFS_DEFAULT_IOSIZE;
else
@@ -490,7 +490,7 @@ cifs_negotiate_rsize(struct cifs_tcon *tcon, struct smb3_fs_context *ctx)
else
defsize = server->maxBuf - sizeof(READ_RSP);
- rsize = ctx->rsize ? ctx->rsize : defsize;
+ rsize = ctx->got_rsize ? ctx->vol_rsize : defsize;
/*
* no CAP_LARGE_READ_X? Then MS-CIFS states that we must limit this to
diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index ff50cdfde5fe4..74bcc51ccd32f 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -467,6 +467,17 @@ smb2_negotiate(const unsigned int xid,
return rc;
}
+static inline unsigned int
+prevent_zero_iosize(unsigned int size, const char *type)
+{
+ if (size == 0) {
+ cifs_dbg(VFS, "SMB: Zero %ssize calculated, using minimum value %u\n",
+ type, CIFS_MIN_DEFAULT_IOSIZE);
+ return CIFS_MIN_DEFAULT_IOSIZE;
+ }
+ return size;
+}
+
static unsigned int
smb2_negotiate_wsize(struct cifs_tcon *tcon, struct smb3_fs_context *ctx)
{
@@ -474,12 +485,12 @@ smb2_negotiate_wsize(struct cifs_tcon *tcon, struct smb3_fs_context *ctx)
unsigned int wsize;
/* start with specified wsize, or default */
- wsize = ctx->wsize ? ctx->wsize : CIFS_DEFAULT_IOSIZE;
+ wsize = ctx->got_wsize ? ctx->vol_wsize : CIFS_DEFAULT_IOSIZE;
wsize = min_t(unsigned int, wsize, server->max_write);
if (!(server->capabilities & SMB2_GLOBAL_CAP_LARGE_MTU))
wsize = min_t(unsigned int, wsize, SMB2_MAX_BUFFER_SIZE);
- return wsize;
+ return prevent_zero_iosize(wsize, "w");
}
static unsigned int
@@ -489,7 +500,7 @@ smb3_negotiate_wsize(struct cifs_tcon *tcon, struct smb3_fs_context *ctx)
unsigned int wsize;
/* start with specified wsize, or default */
- wsize = ctx->wsize ? ctx->wsize : SMB3_DEFAULT_IOSIZE;
+ wsize = ctx->got_wsize ? ctx->vol_wsize : SMB3_DEFAULT_IOSIZE;
wsize = min_t(unsigned int, wsize, server->max_write);
#ifdef CONFIG_CIFS_SMB_DIRECT
if (server->rdma) {
@@ -511,7 +522,7 @@ smb3_negotiate_wsize(struct cifs_tcon *tcon, struct smb3_fs_context *ctx)
if (!(server->capabilities & SMB2_GLOBAL_CAP_LARGE_MTU))
wsize = min_t(unsigned int, wsize, SMB2_MAX_BUFFER_SIZE);
- return wsize;
+ return prevent_zero_iosize(wsize, "w");
}
static unsigned int
@@ -521,13 +532,13 @@ smb2_negotiate_rsize(struct cifs_tcon *tcon, struct smb3_fs_context *ctx)
unsigned int rsize;
/* start with specified rsize, or default */
- rsize = ctx->rsize ? ctx->rsize : CIFS_DEFAULT_IOSIZE;
+ rsize = ctx->got_rsize ? ctx->vol_rsize : CIFS_DEFAULT_IOSIZE;
rsize = min_t(unsigned int, rsize, server->max_read);
if (!(server->capabilities & SMB2_GLOBAL_CAP_LARGE_MTU))
rsize = min_t(unsigned int, rsize, SMB2_MAX_BUFFER_SIZE);
- return rsize;
+ return prevent_zero_iosize(rsize, "r");
}
static unsigned int
@@ -537,7 +548,7 @@ smb3_negotiate_rsize(struct cifs_tcon *tcon, struct smb3_fs_context *ctx)
unsigned int rsize;
/* start with specified rsize, or default */
- rsize = ctx->rsize ? ctx->rsize : SMB3_DEFAULT_IOSIZE;
+ rsize = ctx->got_rsize ? ctx->vol_rsize : SMB3_DEFAULT_IOSIZE;
rsize = min_t(unsigned int, rsize, server->max_read);
#ifdef CONFIG_CIFS_SMB_DIRECT
if (server->rdma) {
@@ -560,7 +571,7 @@ smb3_negotiate_rsize(struct cifs_tcon *tcon, struct smb3_fs_context *ctx)
if (!(server->capabilities & SMB2_GLOBAL_CAP_LARGE_MTU))
rsize = min_t(unsigned int, rsize, SMB2_MAX_BUFFER_SIZE);
- return rsize;
+ return prevent_zero_iosize(rsize, "r");
}
/*
diff --git a/fs/smb/common/smb2pdu.h b/fs/smb/common/smb2pdu.h
index 9f272cc8f5660..0a4ca286f4169 100644
--- a/fs/smb/common/smb2pdu.h
+++ b/fs/smb/common/smb2pdu.h
@@ -95,6 +95,9 @@
*/
#define SMB3_DEFAULT_IOSIZE (4 * 1024 * 1024)
+/* According to MS-SMB2 specification The minimum recommended value is 65536.*/
+#define CIFS_MIN_DEFAULT_IOSIZE (65536)
+
/*
* SMB2 Header Definition
*
--
2.39.5
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