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* [glibc] elf: Fix alloca size in _dl_debug_vdprintf
@ 2022-10-28 10:18 Szabolcs Nagy
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From: Szabolcs Nagy @ 2022-10-28 10:18 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=eef17d4d9fcd38c5cbb9bc9515ba72d1773b67a2
commit eef17d4d9fcd38c5cbb9bc9515ba72d1773b67a2
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date: Tue Oct 11 14:22:35 2022 +0100
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 <fweimer@redhat.com>
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 429d2e80c2..00c114002c 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. */
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2022-10-28 10:18 [glibc] elf: Fix alloca size in _dl_debug_vdprintf Szabolcs Nagy
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