From: Szabolcs Nagy Date: Tue, 11 Oct 2022 13:22:35 +0000 (+0100) Subject: elf: Fix _dl_debug_vdprintf stack buffer underflow X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=059dd1983c8ee1a01c556e3dbe412791f43c2b8a;p=thirdparty%2Fglibc.git elf: Fix _dl_debug_vdprintf stack buffer underflow When printing numbers the alloca buffer size did not consider the optional width parameter for padding. The width is used e.g. by _dl_map_object_from_fd which passes '(int) sizeof (void *) * 2' which can be larger than the buffer size on systems where sizeof (void *) >= 2 * sizeof (unsigned long). But even if large width is not used currently it is better to handle it to avoid surprises. --- diff --git a/elf/dl-printf.c b/elf/dl-printf.c index d3264ba96cd..10efa925bdf 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. */