From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH 11/20] elf: Fix alloca size in _dl_debug_vdprintf
Date: Fri, 28 Oct 2022 15:43:03 +0100 [thread overview]
Message-ID: <Y1vqd03UCGYFyDSi@arm.com> (raw)
In-Reply-To: <21fd200b-951b-2997-a1ce-60e2258aff9b@linaro.org>
The 10/28/2022 10:56, Adhemerval Zanella Netto wrote:
> On 27/10/22 12:33, Szabolcs Nagy via Libc-alpha wrote:
> > 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.
> > ---
> > 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. */
>
>
> Would be better to just limit a maximum width and use a fixed-size buffer instead
> (and assert if size is larger)?
i already committed this. i think it's safe:
it's internal api and using huge paddings is unlikely.
next prev parent reply other threads:[~2022-10-28 14:44 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-27 15:32 [PATCH 00/20] patches from the morello port Szabolcs Nagy
2022-10-27 15:32 ` [PATCH 01/20] Fix OOB read in stdlib thousand grouping parsing [BZ #29727] Szabolcs Nagy
2022-10-27 15:38 ` Andreas Schwab
2022-10-27 15:32 ` [PATCH 02/20] scripts: Use bool in tunables initializer Szabolcs Nagy
2022-10-27 16:29 ` Florian Weimer
2022-10-27 15:32 ` [PATCH 03/20] aarch64: Don't build wordcopy Szabolcs Nagy
2022-10-27 16:59 ` Adhemerval Zanella Netto
2022-10-27 15:32 ` [PATCH 04/20] aarch64: Fix the extension header write in getcontext and swapcontext Szabolcs Nagy
2022-10-28 14:03 ` Adhemerval Zanella Netto
2022-10-27 15:32 ` [PATCH 05/20] Fix invalid pointer dereference in wcscpy_chk Szabolcs Nagy
2022-10-28 5:34 ` Florian Weimer
2022-10-27 15:32 ` [PATCH 06/20] Fix invalid pointer dereference in wcpcpy_chk Szabolcs Nagy
2022-10-28 5:45 ` Florian Weimer
2022-10-27 15:32 ` [PATCH 07/20] Use uintptr_t in fts for pointer alignment Szabolcs Nagy
2022-10-31 16:08 ` Adhemerval Zanella Netto
2022-10-27 15:32 ` [PATCH 08/20] malloc: Use uintptr_t " Szabolcs Nagy
2022-10-31 16:09 ` Adhemerval Zanella Netto
2022-10-27 15:32 ` [PATCH 09/20] malloc: Use uintptr_t in alloc_buffer Szabolcs Nagy
2022-10-27 16:15 ` Florian Weimer
2022-10-27 15:33 ` [PATCH 10/20] malloc: Fix alignment logic in obstack Szabolcs Nagy
2022-10-31 16:14 ` Adhemerval Zanella Netto
2022-11-01 9:43 ` Szabolcs Nagy
2022-11-01 13:07 ` Adhemerval Zanella Netto
2022-10-27 15:33 ` [PATCH 11/20] elf: Fix alloca size in _dl_debug_vdprintf Szabolcs Nagy
2022-10-28 5:31 ` Florian Weimer
2022-10-28 13:56 ` Adhemerval Zanella Netto
2022-10-28 14:43 ` Szabolcs Nagy [this message]
2022-10-28 14:48 ` Adhemerval Zanella Netto
2022-10-27 15:33 ` [PATCH 12/20] Fix the symbolic link of multilib dirs Szabolcs Nagy
2022-10-27 15:33 ` [PATCH 13/20] Use uintptr_t in string/tester for pointer alignment Szabolcs Nagy
2022-10-28 14:11 ` Adhemerval Zanella Netto
2022-10-27 15:33 ` [PATCH 14/20] Fix off-by-one OOB write in iconv/tst-iconv-mt Szabolcs Nagy
2022-10-28 5:39 ` Florian Weimer
2022-10-27 15:33 ` [PATCH 15/20] Fix off-by-one OOB read in elf/tst-tls20 Szabolcs Nagy
2022-10-28 5:36 ` Florian Weimer
2022-10-27 15:33 ` [PATCH 16/20] Fix malloc/tst-scratch_buffer OOB access Szabolcs Nagy
2022-10-28 5:41 ` Florian Weimer
2022-10-28 11:24 ` Szabolcs Nagy
2022-10-28 11:30 ` Florian Weimer
2022-10-28 12:23 ` Szabolcs Nagy
2022-10-28 12:27 ` Florian Weimer
2022-10-27 15:33 ` [PATCH 17/20] Fix missing NUL terminator in stdio-common/scanf13 test Szabolcs Nagy
2022-10-28 5:44 ` Florian Weimer
2022-10-27 15:33 ` [PATCH 18/20] Fix elf/tst-dlmopen-twice to support enough link namespaces Szabolcs Nagy
2022-10-27 16:24 ` Florian Weimer
2022-10-27 16:45 ` Szabolcs Nagy
2022-10-27 16:51 ` Florian Weimer
2022-10-27 16:47 ` Adhemerval Zanella Netto
2022-10-27 15:33 ` [PATCH 19/20] Fix resource/bug-ulimit1 test Szabolcs Nagy
2022-10-27 16:48 ` Adhemerval Zanella Netto
2022-10-27 15:34 ` [PATCH 20/20] Fix stdlib/test-dlclose-exit-race to not hang Szabolcs Nagy
2022-10-27 16:22 ` Florian Weimer
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