From 41416f2330112d29f2cfa337bfc7e672bf0c2768 Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Wed, 15 Apr 2015 16:17:28 -0700 Subject: lib/string_helpers.c: change semantics of string_escape_mem The current semantics of string_escape_mem are inadequate for one of its current users, vsnprintf(). If that is to honour its contract, it must know how much space would be needed for the entire escaped buffer, and string_escape_mem provides no way of obtaining that (short of allocating a large enough buffer (~4 times input string) to let it play with, and that's definitely a big no-no inside vsnprintf). So change the semantics for string_escape_mem to be more snprintf-like: Return the size of the output that would be generated if the destination buffer was big enough, but of course still only write to the part of dst it is allowed to, and (contrary to snprintf) don't do '\0'-termination. It is then up to the caller to detect whether output was truncated and to append a '\0' if desired. Also, we must output partial escape sequences, otherwise a call such as snprintf(buf, 3, "%1pE", "\123") would cause printf to write a \0 to buf[2] but leaving buf[0] and buf[1] with whatever they previously contained. This also fixes a bug in the escaped_string() helper function, which used to unconditionally pass a length of "end-buf" to string_escape_mem(); since the latter doesn't check osz for being insanely large, it would happily write to dst. For example, kasprintf(GFP_KERNEL, "something and then %pE", ...); is an easy way to trigger an oops. In test-string_helpers.c, the -ENOMEM test is replaced with testing for getting the expected return value even if the buffer is too small. We also ensure that nothing is written (by relying on a NULL pointer deref) if the output size is 0 by passing NULL - this has to work for kasprintf("%pE") to work. In net/sunrpc/cache.c, I think qword_add still has the same semantics. Someone should definitely double-check this. In fs/proc/array.c, I made the minimum possible change, but longer-term it should stop poking around in seq_file internals. [andriy.shevchenko@linux.intel.com: simplify qword_add] [andriy.shevchenko@linux.intel.com: add missed curly braces] Signed-off-by: Rasmus Villemoes Acked-by: Andy Shevchenko Signed-off-by: Andy Shevchenko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/string_helpers.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'include') diff --git a/include/linux/string_helpers.h b/include/linux/string_helpers.h index 657571817260..0991913f4953 100644 --- a/include/linux/string_helpers.h +++ b/include/linux/string_helpers.h @@ -47,22 +47,22 @@ static inline int string_unescape_any_inplace(char *buf) #define ESCAPE_ANY_NP (ESCAPE_ANY | ESCAPE_NP) #define ESCAPE_HEX 0x20 -int string_escape_mem(const char *src, size_t isz, char **dst, size_t osz, +int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz, unsigned int flags, const char *esc); static inline int string_escape_mem_any_np(const char *src, size_t isz, - char **dst, size_t osz, const char *esc) + char *dst, size_t osz, const char *esc) { return string_escape_mem(src, isz, dst, osz, ESCAPE_ANY_NP, esc); } -static inline int string_escape_str(const char *src, char **dst, size_t sz, +static inline int string_escape_str(const char *src, char *dst, size_t sz, unsigned int flags, const char *esc) { return string_escape_mem(src, strlen(src), dst, sz, flags, esc); } -static inline int string_escape_str_any_np(const char *src, char **dst, +static inline int string_escape_str_any_np(const char *src, char *dst, size_t sz, const char *esc) { return string_escape_str(src, dst, sz, ESCAPE_ANY_NP, esc); -- cgit v1.2.3