From b32a09db4fb9a87246ba4e7726a979ac4709ad97 Mon Sep 17 00:00:00 2001 From: Markus Armbruster Date: Tue, 26 Feb 2008 09:57:11 -0600 Subject: [PATCH] add match_strlcpy() us it to make v9fs make uname and remotename parsing more robust match_strcpy() is a somewhat creepy function: the caller needs to make sure that the destination buffer is big enough, and when he screws up or forgets, match_strcpy() happily overruns the buffer. There's exactly one customer: v9fs_parse_options(). I believe it currently can't overflow its buffer, but that's not exactly obvious. The source string is a substing of the mount options. The kernel silently truncates those to PAGE_SIZE bytes, including the terminating zero. See compat_sys_mount() and do_mount(). The destination buffer is obtained from __getname(), which allocates from name_cachep, which is initialized by vfs_caches_init() for size PATH_MAX. We're safe as long as PATH_MAX <= PAGE_SIZE. PATH_MAX is 4096. As far as I know, the smallest PAGE_SIZE is also 4096. Here's a patch that makes the code a bit more obviously correct. It doesn't depend on PATH_MAX <= PAGE_SIZE. Signed-off-by: Markus Armbruster Cc: Latchesar Ionkov Cc: Jim Meyering Cc: "Randy.Dunlap" Signed-off-by: Andrew Morton Signed-off-by: Eric Van Hensbergen --- fs/9p/v9fs.c | 4 ++-- include/linux/parser.h | 2 +- lib/parser.c | 32 ++++++++++++++++++++------------ 3 files changed, 23 insertions(+), 15 deletions(-) diff --git a/fs/9p/v9fs.c b/fs/9p/v9fs.c index 9b0f0222e8b..e307fbd34fa 100644 --- a/fs/9p/v9fs.c +++ b/fs/9p/v9fs.c @@ -125,10 +125,10 @@ static void v9fs_parse_options(struct v9fs_session_info *v9ses) v9ses->afid = option; break; case Opt_uname: - match_strcpy(v9ses->uname, &args[0]); + match_strlcpy(v9ses->uname, &args[0], PATH_MAX); break; case Opt_remotename: - match_strcpy(v9ses->aname, &args[0]); + match_strlcpy(v9ses->aname, &args[0], PATH_MAX); break; case Opt_nodevmap: v9ses->nodev = 1; diff --git a/include/linux/parser.h b/include/linux/parser.h index 26b2bdfcaf0..7dcd0507575 100644 --- a/include/linux/parser.h +++ b/include/linux/parser.h @@ -29,5 +29,5 @@ int match_token(char *, match_table_t table, substring_t args[]); int match_int(substring_t *, int *result); int match_octal(substring_t *, int *result); int match_hex(substring_t *, int *result); -void match_strcpy(char *, const substring_t *); +size_t match_strlcpy(char *, const substring_t *, size_t); char *match_strdup(const substring_t *); diff --git a/lib/parser.c b/lib/parser.c index 703c8c13b34..4f0cbc03e0e 100644 --- a/lib/parser.c +++ b/lib/parser.c @@ -182,18 +182,25 @@ int match_hex(substring_t *s, int *result) } /** - * match_strcpy: - copies the characters from a substring_t to a string - * @to: string to copy characters to. - * @s: &substring_t to copy + * match_strlcpy: - Copy the characters from a substring_t to a sized buffer + * @dest: where to copy to + * @src: &substring_t to copy + * @size: size of destination buffer * - * Description: Copies the set of characters represented by the given - * &substring_t @s to the c-style string @to. Caller guarantees that @to is - * large enough to hold the characters of @s. + * Description: Copy the characters in &substring_t @src to the + * c-style string @dest. Copy no more than @size - 1 characters, plus + * the terminating NUL. Return length of @src. */ -void match_strcpy(char *to, const substring_t *s) +size_t match_strlcpy(char *dest, const substring_t *src, size_t size) { - memcpy(to, s->from, s->to - s->from); - to[s->to - s->from] = '\0'; + size_t ret = src->to - src->from; + + if (size) { + size_t len = ret >= size ? size - 1 : ret; + memcpy(dest, src->from, len); + dest[len] = '\0'; + } + return ret; } /** @@ -206,9 +213,10 @@ void match_strcpy(char *to, const substring_t *s) */ char *match_strdup(const substring_t *s) { - char *p = kmalloc(s->to - s->from + 1, GFP_KERNEL); + size_t sz = s->to - s->from + 1; + char *p = kmalloc(sz, GFP_KERNEL); if (p) - match_strcpy(p, s); + match_strlcpy(p, s, sz); return p; } @@ -216,5 +224,5 @@ EXPORT_SYMBOL(match_token); EXPORT_SYMBOL(match_int); EXPORT_SYMBOL(match_octal); EXPORT_SYMBOL(match_hex); -EXPORT_SYMBOL(match_strcpy); +EXPORT_SYMBOL(match_strlcpy); EXPORT_SYMBOL(match_strdup); -- 2.41.1