smb: client: Store original IO parameters and prevent zero IO sizes

[ 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@huawei.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
index e38521a713a6b3a299d0ed9e8feacdc0d2cb365e..00af8dd5aa68906e57496feefc43573081440bb4 100644 (file)
--- a/fs/smb/client/fs_context.c
+++ b/fs/smb/client/fs_context.c
@@ -1327,6 +1327,7 @@ 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;
@@ -1342,6 +1343,7 @@ 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 881bfc08667e7d9d5b78516d0262f073b0ff4ce9..7516ccdc69c71ca1e3d681771b547652e25229a8 100644 (file)
--- a/fs/smb/client/fs_context.h
+++ b/fs/smb/client/fs_context.h
@@ -279,6 +279,9 @@ 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 e28cdaca47e1204bd4fc79fc57c262890cee2ddd..73a689b4ccdff0a880a4b41d18b9b3ca3f1f77a1 100644 (file)
--- 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 6f89e087629fe67e198808d65df5db966d32f2a4..6795970d4de6e4b55605c99d0b2bac6ecf4ed1a2 100644 (file)
--- 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 12f0013334057e42d455a5c6d35d8b6b7ac41c0a..f79a5165a7cc6a22b4aecedca75ecf6e86751aaf 100644 (file)
--- 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
  *