From: Wang Zhaolong wangzhaolong1@huawei.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@huawei.com Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Sasha Levin sashal@kernel.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 e38521a713a6b..00af8dd5aa689 100644 --- 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 881bfc08667e7..7516ccdc69c71 100644 --- 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 e28cdaca47e12..73a689b4ccdff 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 6f89e087629fe..6795970d4de6e 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 12f0013334057..f79a5165a7cc6 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 *