cifs: replace various strncpy with strscpy and similar

Using strscpy is cleaner, and avoids some problems with
handling maximum length strings.  Linus noticed the
original problem and Aurelien pointed out some additional
problems. Fortunately most of this is SMB1 code (and
in particular the ASCII string handling older, which
is less common).

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

6 files changed, 112 insertions, 146 deletions

diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index e23234207fc2..592a6cea2b79 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -579,6 +579,7 @@ extern void rqst_page_get_length(struct smb_rqst *rqst, unsigned int page,
                                 unsigned int *len, unsigned int *offset);
 
 void extract_unc_hostname(const char *unc, const char **h, size_t *len);
+int copy_path_name(char *dst, const char *src);
 
 #ifdef CONFIG_CIFS_DFS_UPCALL
 static inline int get_dfs_path(const unsigned int xid, struct cifs_ses *ses,
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index e2f95965065d..3907653e63c7 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -942,10 +942,8 @@ PsxDelete:
                                        PATH_MAX, nls_codepage, remap);
                 name_len++;     /* trailing null */
                 name_len *= 2;
-        } else { /* BB add path length overrun check */
-                name_len = strnlen(fileName, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->FileName, fileName, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->FileName, fileName);
         }
 
         params = 6 + name_len;
@@ -1015,10 +1013,8 @@ DelFileRetry:
                                               remap);
                 name_len++;     /* trailing null */
                 name_len *= 2;
-        } else {                /* BB improve check for buffer overruns BB */
-                name_len = strnlen(name, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->fileName, name, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->fileName, name);
         }
         pSMB->SearchAttributes =
             cpu_to_le16(ATTR_READONLY | ATTR_HIDDEN | ATTR_SYSTEM);
@@ -1062,10 +1058,8 @@ RmDirRetry:
                                               remap);
                 name_len++;     /* trailing null */
                 name_len *= 2;
-        } else {                /* BB improve check for buffer overruns BB */
-                name_len = strnlen(name, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->DirName, name, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->DirName, name);
         }
 
         pSMB->BufferFormat = 0x04;
@@ -1107,10 +1101,8 @@ MkDirRetry:
                                               remap);
                 name_len++;     /* trailing null */
                 name_len *= 2;
-        } else {                /* BB improve check for buffer overruns BB */
-                name_len = strnlen(name, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->DirName, name, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->DirName, name);
         }
 
         pSMB->BufferFormat = 0x04;
@@ -1157,10 +1149,8 @@ PsxCreat:
                                        PATH_MAX, nls_codepage, remap);
                 name_len++;     /* trailing null */
                 name_len *= 2;
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(name, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->FileName, name, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->FileName, name);
         }
 
         params = 6 + name_len;
@@ -1324,11 +1314,9 @@ OldOpenRetry:
                                       fileName, PATH_MAX, nls_codepage, remap);
                 name_len++;     /* trailing null */
                 name_len *= 2;
-        } else {                /* BB improve check for buffer overruns BB */
+        } else {
                 count = 0;      /* no pad */
-                name_len = strnlen(fileName, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->fileName, fileName, name_len);
+                name_len = copy_path_name(pSMB->fileName, fileName);
         }
         if (*pOplock & REQ_OPLOCK)
                 pSMB->OpenFlags = cpu_to_le16(REQ_OPLOCK);
@@ -1442,11 +1430,8 @@ openRetry:
                 /* BB improve check for buffer overruns BB */
                 /* no pad */
                 count = 0;
-                name_len = strnlen(path, PATH_MAX);
-                /* trailing null */
-                name_len++;
+                name_len = copy_path_name(req->fileName, path);
                 req->NameLength = cpu_to_le16(name_len);
-                strncpy(req->fileName, path, name_len);
         }
 
         if (*oplock & REQ_OPLOCK)
@@ -2812,15 +2797,10 @@ renameRetry:
                                        remap);
                 name_len2 += 1 /* trailing null */  + 1 /* Signature word */ ;
                 name_len2 *= 2; /* convert to bytes */
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(from_name, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->OldFileName, from_name, name_len);
-                name_len2 = strnlen(to_name, PATH_MAX);
-                name_len2++;    /* trailing null */
+        } else {
+                name_len = copy_path_name(pSMB->OldFileName, from_name);
+                name_len2 = copy_path_name(pSMB->OldFileName+name_len+1, to_name);
                 pSMB->OldFileName[name_len] = 0x04;  /* 2nd buffer format */
-                strncpy(&pSMB->OldFileName[name_len + 1], to_name, name_len2);
-                name_len2++;    /* trailing null */
                 name_len2++;    /* signature byte */
         }
 
@@ -2962,15 +2942,10 @@ copyRetry:
                                        toName, PATH_MAX, nls_codepage, remap);
                 name_len2 += 1 /* trailing null */  + 1 /* Signature word */ ;
                 name_len2 *= 2; /* convert to bytes */
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(fromName, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->OldFileName, fromName, name_len);
-                name_len2 = strnlen(toName, PATH_MAX);
-                name_len2++;    /* trailing null */
+        } else {
+                name_len = copy_path_name(pSMB->OldFileName, fromName);
                 pSMB->OldFileName[name_len] = 0x04;  /* 2nd buffer format */
-                strncpy(&pSMB->OldFileName[name_len + 1], toName, name_len2);
-                name_len2++;    /* trailing null */
+                name_len2 = copy_path_name(pSMB->OldFileName+name_len+1, toName);
                 name_len2++;    /* signature byte */
         }
 
@@ -3021,10 +2996,8 @@ createSymLinkRetry:
                 name_len++;     /* trailing null */
                 name_len *= 2;
 
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(fromName, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->FileName, fromName, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->FileName, fromName);
         }
         params = 6 + name_len;
         pSMB->MaxSetupCount = 0;
@@ -3044,10 +3017,8 @@ createSymLinkRetry:
                                         PATH_MAX, nls_codepage, remap);
                 name_len_target++;      /* trailing null */
                 name_len_target *= 2;
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len_target = strnlen(toName, PATH_MAX);
-                name_len_target++;      /* trailing null */
-                strncpy(data_offset, toName, name_len_target);
+        } else {
+                name_len_target = copy_path_name(data_offset, toName);
         }
 
         pSMB->MaxParameterCount = cpu_to_le16(2);
@@ -3109,10 +3080,8 @@ createHardLinkRetry:
                 name_len++;     /* trailing null */
                 name_len *= 2;
 
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(toName, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->FileName, toName, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->FileName, toName);
         }
         params = 6 + name_len;
         pSMB->MaxSetupCount = 0;
@@ -3131,10 +3100,8 @@ createHardLinkRetry:
                                        PATH_MAX, nls_codepage, remap);
                 name_len_target++;      /* trailing null */
                 name_len_target *= 2;
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len_target = strnlen(fromName, PATH_MAX);
-                name_len_target++;      /* trailing null */
-                strncpy(data_offset, fromName, name_len_target);
+        } else {
+                name_len_target = copy_path_name(data_offset, fromName);
         }
 
         pSMB->MaxParameterCount = cpu_to_le16(2);
@@ -3213,15 +3180,10 @@ winCreateHardLinkRetry:
                                        remap);
                 name_len2 += 1 /* trailing null */  + 1 /* Signature word */ ;
                 name_len2 *= 2; /* convert to bytes */
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(from_name, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->OldFileName, from_name, name_len);
-                name_len2 = strnlen(to_name, PATH_MAX);
-                name_len2++;    /* trailing null */
+        } else {
+                name_len = copy_path_name(pSMB->OldFileName, from_name);
                 pSMB->OldFileName[name_len] = 0x04;     /* 2nd buffer format */
-                strncpy(&pSMB->OldFileName[name_len + 1], to_name, name_len2);
-                name_len2++;    /* trailing null */
+                name_len2 = copy_path_name(pSMB->OldFileName+name_len+1, to_name);
                 name_len2++;    /* signature byte */
         }
 
@@ -3271,10 +3233,8 @@ querySymLinkRetry:
                                            remap);
                 name_len++;     /* trailing null */
                 name_len *= 2;
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(searchName, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->FileName, searchName, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->FileName, searchName);
         }
 
         params = 2 /* level */  + 4 /* rsrvd */  + name_len /* incl null */ ;
@@ -3691,10 +3651,8 @@ queryAclRetry:
                 name_len *= 2;
                 pSMB->FileName[name_len] = 0;
                 pSMB->FileName[name_len+1] = 0;
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(searchName, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->FileName, searchName, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->FileName, searchName);
         }
 
         params = 2 /* level */  + 4 /* rsrvd */  + name_len /* incl null */ ;
@@ -3776,10 +3734,8 @@ setAclRetry:
                                            PATH_MAX, nls_codepage, remap);
                 name_len++;     /* trailing null */
                 name_len *= 2;
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(fileName, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->FileName, fileName, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->FileName, fileName);
         }
         params = 6 + name_len;
         pSMB->MaxParameterCount = cpu_to_le16(2);
@@ -4184,9 +4140,7 @@ QInfRetry:
                 name_len++;     /* trailing null */
                 name_len *= 2;
         } else {
-                name_len = strnlen(search_name, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->FileName, search_name, name_len);
+                name_len = copy_path_name(pSMB->FileName, search_name);
         }
         pSMB->BufferFormat = 0x04;
         name_len++; /* account for buffer type byte */
@@ -4321,10 +4275,8 @@ QPathInfoRetry:
                                        PATH_MAX, nls_codepage, remap);
                 name_len++;     /* trailing null */
                 name_len *= 2;
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(search_name, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->FileName, search_name, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->FileName, search_name);
         }
 
         params = 2 /* level */ + 4 /* reserved */ + name_len /* includes NUL */;
@@ -4490,10 +4442,8 @@ UnixQPathInfoRetry:
                                        PATH_MAX, nls_codepage, remap);
                 name_len++;     /* trailing null */
                 name_len *= 2;
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(searchName, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->FileName, searchName, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->FileName, searchName);
         }
 
         params = 2 /* level */ + 4 /* reserved */ + name_len /* includes NUL */;
@@ -4593,17 +4543,16 @@ findFirstRetry:
                         pSMB->FileName[name_len+1] = 0;
                         name_len += 2;
                 }
-        } else {        /* BB add check for overrun of SMB buf BB */
-                name_len = strnlen(searchName, PATH_MAX);
-/* BB fix here and in unicode clause above ie
-                if (name_len > buffersize-header)
-                        free buffer exit; BB */
-                strncpy(pSMB->FileName, searchName, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->FileName, searchName);
                 if (msearch) {
-                        pSMB->FileName[name_len] = CIFS_DIR_SEP(cifs_sb);
-                        pSMB->FileName[name_len+1] = '*';
-                        pSMB->FileName[name_len+2] = 0;
-                        name_len += 3;
+                        if (WARN_ON_ONCE(name_len > PATH_MAX-2))
+                                name_len = PATH_MAX-2;
+                        /* overwrite nul byte */
+                        pSMB->FileName[name_len-1] = CIFS_DIR_SEP(cifs_sb);
+                        pSMB->FileName[name_len] = '*';
+                        pSMB->FileName[name_len+1] = 0;
+                        name_len += 2;
                 }
         }
 
@@ -4898,10 +4847,8 @@ GetInodeNumberRetry:
                                            remap);
                 name_len++;     /* trailing null */
                 name_len *= 2;
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(search_name, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->FileName, search_name, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->FileName, search_name);
         }
 
         params = 2 /* level */  + 4 /* rsrvd */  + name_len /* incl null */ ;
@@ -5008,9 +4955,7 @@ getDFSRetry:
                 name_len++;     /* trailing null */
                 name_len *= 2;
         } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(search_name, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->RequestFileName, search_name, name_len);
+                name_len = copy_path_name(pSMB->RequestFileName, search_name);
         }
 
         if (ses->server->sign)
@@ -5663,10 +5608,8 @@ SetEOFRetry:
                                        PATH_MAX, cifs_sb->local_nls, remap);
                 name_len++;     /* trailing null */
                 name_len *= 2;
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(file_name, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->FileName, file_name, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->FileName, file_name);
         }
         params = 6 + name_len;
         data_count = sizeof(struct file_end_of_file_info);
@@ -5959,10 +5902,8 @@ SetTimesRetry:
                                        PATH_MAX, nls_codepage, remap);
                 name_len++;     /* trailing null */
                 name_len *= 2;
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(fileName, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->FileName, fileName, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->FileName, fileName);
         }
 
         params = 6 + name_len;
@@ -6040,10 +5981,8 @@ SetAttrLgcyRetry:
                                        PATH_MAX, nls_codepage);
                 name_len++;     /* trailing null */
                 name_len *= 2;
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(fileName, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->fileName, fileName, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->fileName, fileName);
         }
         pSMB->attr = cpu_to_le16(dos_attrs);
         pSMB->BufferFormat = 0x04;
@@ -6203,10 +6142,8 @@ setPermsRetry:
                                        PATH_MAX, nls_codepage, remap);
                 name_len++;     /* trailing null */
                 name_len *= 2;
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(file_name, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->FileName, file_name, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->FileName, file_name);
         }
 
         params = 6 + name_len;
@@ -6298,10 +6235,8 @@ QAllEAsRetry:
                                        PATH_MAX, nls_codepage, remap);
                 list_len++;     /* trailing null */
                 list_len *= 2;
-        } else {        /* BB improve the check for buffer overruns BB */
-                list_len = strnlen(searchName, PATH_MAX);
-                list_len++;     /* trailing null */
-                strncpy(pSMB->FileName, searchName, list_len);
+        } else {
+                list_len = copy_path_name(pSMB->FileName, searchName);
         }
 
         params = 2 /* level */ + 4 /* reserved */ + list_len /* includes NUL */;
@@ -6480,10 +6415,8 @@ SetEARetry:
                                        PATH_MAX, nls_codepage, remap);
                 name_len++;     /* trailing null */
                 name_len *= 2;
-        } else {        /* BB improve the check for buffer overruns BB */
-                name_len = strnlen(fileName, PATH_MAX);
-                name_len++;     /* trailing null */
-                strncpy(pSMB->FileName, fileName, name_len);
+        } else {
+                name_len = copy_path_name(pSMB->FileName, fileName);
         }
 
         params = 6 + name_len;
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index ddefddeffd06..5299effa6f7d 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -4231,16 +4231,19 @@ build_unc_path_to_root(const struct smb_vol *vol,
                 strlen(vol->prepath) + 1 : 0;
         unsigned int unc_len = strnlen(vol->UNC, MAX_TREE_SIZE + 1);
 
+        if (unc_len > MAX_TREE_SIZE)
+                return ERR_PTR(-EINVAL);
+
         full_path = kmalloc(unc_len + pplen + 1, GFP_KERNEL);
         if (full_path == NULL)
                 return ERR_PTR(-ENOMEM);
 
-        strncpy(full_path, vol->UNC, unc_len);
+        memcpy(full_path, vol->UNC, unc_len);
         pos = full_path + unc_len;
 
         if (pplen) {
                 *pos = CIFS_DIR_SEP(cifs_sb);
-                strncpy(pos + 1, vol->prepath, pplen);
+                memcpy(pos + 1, vol->prepath, pplen);
                 pos += pplen;
         }
 
diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index f26a48dd2e39..be424e81e3ad 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -69,11 +69,10 @@ cifs_build_path_to_root(struct smb_vol *vol, struct cifs_sb_info *cifs_sb,
                 return full_path;
 
         if (dfsplen)
-                strncpy(full_path, tcon->treeName, dfsplen);
+                memcpy(full_path, tcon->treeName, dfsplen);
         full_path[dfsplen] = CIFS_DIR_SEP(cifs_sb);
-        strncpy(full_path + dfsplen + 1, vol->prepath, pplen);
+        memcpy(full_path + dfsplen + 1, vol->prepath, pplen);
         convert_delimiter(full_path, CIFS_DIR_SEP(cifs_sb));
-        full_path[dfsplen + pplen] = 0; /* add trailing null */
         return full_path;
 }
 
diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index f383877a6511..5ad83bdb9bea 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -1011,3 +1011,25 @@ void extract_unc_hostname(const char *unc, const char **h, size_t *len)
         *h = unc;
         *len = end - unc;
 }
+
+/**
+ * copy_path_name - copy src path to dst, possibly truncating
+ *
+ * returns number of bytes written (including trailing nul)
+ */
+int copy_path_name(char *dst, const char *src)
+{
+        int name_len;
+
+        /*
+         * PATH_MAX includes nul, so if strlen(src) >= PATH_MAX it
+         * will truncate and strlen(dst) will be PATH_MAX-1
+         */
+        name_len = strscpy(dst, src, PATH_MAX);
+        if (WARN_ON_ONCE(name_len < 0))
+                name_len = PATH_MAX-1;
+
+        /* we count the trailing nul */
+        name_len++;
+        return name_len;
+}
diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index dcd49ad60c83..4c764ff7edd2 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -159,13 +159,16 @@ static void ascii_ssetup_strings(char **pbcc_area, struct cifs_ses *ses,
                                  const struct nls_table *nls_cp)
 {
         char *bcc_ptr = *pbcc_area;
+        int len;
 
         /* copy user */
         /* BB what about null user mounts - check that we do this BB */
         /* copy user */
         if (ses->user_name != NULL) {
-                strncpy(bcc_ptr, ses->user_name, CIFS_MAX_USERNAME_LEN);
-                bcc_ptr += strnlen(ses->user_name, CIFS_MAX_USERNAME_LEN);
+                len = strscpy(bcc_ptr, ses->user_name, CIFS_MAX_USERNAME_LEN);
+                if (WARN_ON_ONCE(len < 0))
+                        len = CIFS_MAX_USERNAME_LEN - 1;
+                bcc_ptr += len;
         }
         /* else null user mount */
         *bcc_ptr = 0;
@@ -173,8 +176,10 @@ static void ascii_ssetup_strings(char **pbcc_area, struct cifs_ses *ses,
 
         /* copy domain */
         if (ses->domainName != NULL) {
-                strncpy(bcc_ptr, ses->domainName, CIFS_MAX_DOMAINNAME_LEN);
-                bcc_ptr += strnlen(ses->domainName, CIFS_MAX_DOMAINNAME_LEN);
+                len = strscpy(bcc_ptr, ses->domainName, CIFS_MAX_DOMAINNAME_LEN);
+                if (WARN_ON_ONCE(len < 0))
+                        len = CIFS_MAX_DOMAINNAME_LEN - 1;
+                bcc_ptr += len;
         } /* else we will send a null domain name
              so the server will default to its own domain */
         *bcc_ptr = 0;
@@ -242,9 +247,10 @@ static void decode_ascii_ssetup(char **pbcc_area, __u16 bleft,
 
         kfree(ses->serverOS);
 
-        ses->serverOS = kzalloc(len + 1, GFP_KERNEL);
+        ses->serverOS = kmalloc(len + 1, GFP_KERNEL);
         if (ses->serverOS) {
-                strncpy(ses->serverOS, bcc_ptr, len);
+                memcpy(ses->serverOS, bcc_ptr, len);
+                ses->serverOS[len] = 0;
                 if (strncmp(ses->serverOS, "OS/2", 4) == 0)
                         cifs_dbg(FYI, "OS/2 server\n");
         }
@@ -258,9 +264,11 @@ static void decode_ascii_ssetup(char **pbcc_area, __u16 bleft,
 
         kfree(ses->serverNOS);
 
-        ses->serverNOS = kzalloc(len + 1, GFP_KERNEL);
-        if (ses->serverNOS)
-                strncpy(ses->serverNOS, bcc_ptr, len);
+        ses->serverNOS = kmalloc(len + 1, GFP_KERNEL);
+        if (ses->serverNOS) {
+                memcpy(ses->serverNOS, bcc_ptr, len);
+                ses->serverNOS[len] = 0;
+        }
 
         bcc_ptr += len + 1;
         bleft -= len + 1;