mount.cifs can pass a device with multiple delimiters in it. This will cause rename(2) to fail with ENOENT.
V2: - Make sanitize_path more readable. - Fix multiple delimiters between UNC and prepath. - Avoid a memory leak if a bad user starts putting a lot of delimiters in the path on purpose.
BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=2031200 Fixes: 24e0a1eff9e2 ("cifs: switch to new mount api") Cc: stable@vger.kernel.org # 5.11+ Signed-off-by: Thiago Rafael Becker trbecker@gmail.com --- fs/cifs/fs_context.c | 38 +++++++++++++++++++++++++++++++++++++- 1 file changed, 37 insertions(+), 1 deletion(-)
diff --git a/fs/cifs/fs_context.c b/fs/cifs/fs_context.c index 6a179ae753c1..e3ed25dc6f3f 100644 --- a/fs/cifs/fs_context.c +++ b/fs/cifs/fs_context.c @@ -434,6 +434,42 @@ int smb3_parse_opt(const char *options, const char *key, char **val) return rc; }
+/* + * Remove duplicate path delimiters. Windows is supposed to do that + * but there are some bugs that prevent rename from working if there are + * multiple delimiters. + * + * Returns a sanitized duplicate of @path. The caller is responsible for + * cleaning up the original. + */ +#define IS_DELIM(c) ((c) == '/' || (c) == '\') +static char *sanitize_path(char *path) +{ + char *cursor1 = path, *cursor2 = path; + + /* skip all prepended delimiters */ + while (IS_DELIM(*cursor1)) + cursor1++; + + /* copy the first letter */ + *cursor2 = *cursor1; + + /* copy the remainder... */ + while (*(cursor1++)) { + /* ... skipping all duplicated delimiters */ + if (IS_DELIM(*cursor1) && IS_DELIM(*cursor2)) + continue; + *(++cursor2) = *cursor1; + } + + /* if the last character is a delimiter, skip it */ + if (IS_DELIM(*(cursor2 - 1))) + cursor2--; + + *(cursor2) = '\0'; + return kstrdup(path, GFP_KERNEL); +} + /* * Parse a devname into substrings and populate the ctx->UNC and ctx->prepath * fields with the result. Returns 0 on success and an error otherwise @@ -493,7 +529,7 @@ smb3_parse_devname(const char *devname, struct smb3_fs_context *ctx) if (!*pos) return 0;
- ctx->prepath = kstrdup(pos, GFP_KERNEL); + ctx->prepath = sanitize_path(pos); if (!ctx->prepath) return -ENOMEM;