Messages in this thread Patch in this message |  | | From | "Masami Hiramatsu (Google)" <> | | Subject | [PATCH v6 2/2] lib/vsprintf: Limit the returning size to INT_MAX | | Date | Thu, 26 Mar 2026 21:12:10 +0900 |
| |
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
The return value of vsnprintf() and bstr_printf() can overflow INT_MAX and return a minus value. In the @size is checked input overflow, but it does not check the output, which is expected required size.
This should never happen but it should be checked and limited.
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> --- Changes in v5: - Fix bstr_printf() too. Changes in v4: - Add Petr's reviewed-by. (Thanks!) Changes in v3: - Use local variable for better readability. --- lib/vsprintf.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 10a1b21c8920..d0aa6b34f0e4 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -2856,6 +2856,7 @@ static unsigned long long convert_num_spec(unsigned int val, int size, struct pr int vsnprintf(char *buf, size_t size, const char *fmt_str, va_list args) { char *str, *end; + size_t ret_size; struct printf_spec spec = {0}; struct fmt fmt = { .str = fmt_str, @@ -2975,8 +2976,12 @@ int vsnprintf(char *buf, size_t size, const char *fmt_str, va_list args) } /* the trailing null byte doesn't count towards the total */ - return str-buf; + ret_size = str - buf; + /* Make sure the return value is within the positive integer range */ + if (WARN_ON_ONCE(ret_size > INT_MAX)) + ret_size = INT_MAX; + return ret_size; } EXPORT_SYMBOL(vsnprintf); @@ -3280,6 +3285,7 @@ int bstr_printf(char *buf, size_t size, const char *fmt_str, const u32 *bin_buf) struct printf_spec spec = {0}; char *str, *end; const char *args = (const char *)bin_buf; + size_t ret_size; if (WARN_ON_ONCE(size > INT_MAX)) return 0; @@ -3428,7 +3434,12 @@ int bstr_printf(char *buf, size_t size, const char *fmt_str, const u32 *bin_buf) #undef get_arg /* the trailing null byte doesn't count towards the total */ - return str - buf; + ret_size = str - buf; + + /* Make sure the return value is within the positive integer range */ + if (WARN_ON_ONCE(ret_size > INT_MAX)) + ret_size = INT_MAX; + return ret_size; } EXPORT_SYMBOL_GPL(bstr_printf);
|  |