[glibc/arm/morello/main] elf: Fix _dl_debug_vdprintf stack buffer underflow

[Szabolcs Nagy <nsz@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=059dd1983c8ee1a01c556e3dbe412791f43c2b8a

commit 059dd1983c8ee1a01c556e3dbe412791f43c2b8a
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Tue Oct 11 14:22:35 2022 +0100

    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:
---
 elf/dl-printf.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/elf/dl-printf.c b/elf/dl-printf.c
index d3264ba96c..10efa925bd 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.  */