From: Szabolcs Nagy Date: Tue, 11 Oct 2022 13:22:35 +0000 (+0100) Subject: elf: Fix alloca size in _dl_debug_vdprintf X-Git-Tag: glibc-2.37~209 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=eef17d4d9fcd38c5cbb9bc9515ba72d1773b67a2;p=thirdparty%2Fglibc.git elf: Fix alloca size in _dl_debug_vdprintf The alloca size did not consider the optional width parameter for padding which could cause buffer underflow. The width is currently used e.g. by _dl_map_object_from_fd which passes 2 * sizeof(void *) which can be larger than the alloca buffer size on targets where sizeof(void *) >= 2 * sizeof(unsigned long). Even if large width is not used on existing targets it is better to fix the formatting code to avoid surprises. Reviewed-by: Florian Weimer --- diff --git a/elf/dl-printf.c b/elf/dl-printf.c index 429d2e80c2b..00c114002c8 100644 --- a/elf/dl-printf.c +++ b/elf/dl-printf.c @@ -163,8 +163,11 @@ _dl_debug_vdprintf (int fd, int tag_p, const char *fmt, va_list arg) /* We use alloca() to allocate the buffer with the most pessimistic guess for the size. Using alloca() allows having more than one integer formatting in a call. */ - char *buf = (char *) alloca (1 + 3 * sizeof (unsigned long int)); - char *endp = &buf[1 + 3 * sizeof (unsigned long int)]; + int size = 1 + 3 * sizeof (unsigned long int); + if (width + 1 > size) + size = width + 1; + char *buf = (char *) alloca (size); + char *endp = &buf[size]; char *cp = _itoa (num, endp, *fmt == 'x' ? 16 : 10, 0); /* Pad to the width the user specified. */