* [PATCH v2] vfprintf-internal: Replace alloca with malloc.
@ 2023-05-10 15:32 Joe Simmons-Talbott
2023-05-15 18:35 ` Carlos O'Donell
0 siblings, 1 reply; 3+ messages in thread
From: Joe Simmons-Talbott @ 2023-05-10 15:32 UTC (permalink / raw)
To: libc-alpha; +Cc: Joe Simmons-Talbott
Avoid potential stack overflow from unbounded alloca.
---
Changes to v1:
* Don't check pointer before calling free()
* Move deallocation code after the all_done label
stdio-common/vfprintf-internal.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/stdio-common/vfprintf-internal.c b/stdio-common/vfprintf-internal.c
index c76c06e49b..58c21481ce 100644
--- a/stdio-common/vfprintf-internal.c
+++ b/stdio-common/vfprintf-internal.c
@@ -1001,6 +1001,7 @@ printf_positional (struct Xprintf_buffer * buf, const CHAR_T *format,
scratch_buffer_init (&specsbuf);
struct printf_spec *specs = specsbuf.data;
size_t specs_limit = specsbuf.length / sizeof (specs[0]);
+ bool malloced_pa_user = false;
/* Used as a backing store for args_value, args_size, args_type
below. */
@@ -1171,7 +1172,10 @@ printf_positional (struct Xprintf_buffer * buf, const CHAR_T *format,
else if (__glibc_unlikely (__printf_va_arg_table != NULL)
&& __printf_va_arg_table[args_type[cnt] - PA_LAST] != NULL)
{
- args_value[cnt].pa_user = alloca (args_size[cnt]);
+ args_value[cnt].pa_user = malloc (args_size[cnt]);
+ if (args_value[cnt].pa_user == NULL)
+ break;
+ malloced_pa_user = true;
(*__printf_va_arg_table[args_type[cnt] - PA_LAST])
(args_value[cnt].pa_user, ap_savep);
}
@@ -1334,7 +1338,11 @@ printf_positional (struct Xprintf_buffer * buf, const CHAR_T *format,
(specs[nspecs_done].next_fmt
- specs[nspecs_done].end_of_fmt));
}
all_done:
+ if (malloced_pa_user)
+ for (cnt = 0; cnt < nargs; ++cnt)
+ free (args_value[cnt].pa_user);
scratch_buffer_free (&argsbuf);
scratch_buffer_free (&specsbuf);
}
--
2.39.2
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] vfprintf-internal: Replace alloca with malloc.
2023-05-10 15:32 [PATCH v2] vfprintf-internal: Replace alloca with malloc Joe Simmons-Talbott
@ 2023-05-15 18:35 ` Carlos O'Donell
2023-05-15 18:49 ` Joe Simmons-Talbott
0 siblings, 1 reply; 3+ messages in thread
From: Carlos O'Donell @ 2023-05-15 18:35 UTC (permalink / raw)
To: Joe Simmons-Talbott, libc-alpha
On 5/10/23 11:32, Joe Simmons-Talbott via Libc-alpha wrote:
> Avoid potential stack overflow from unbounded alloca.
This fails to apply in pre-commit CI e.g. error: corrupt patch at line 145
How did you generate this patch?
> ---
> Changes to v1:
> * Don't check pointer before calling free()
> * Move deallocation code after the all_done label
>
> stdio-common/vfprintf-internal.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/stdio-common/vfprintf-internal.c b/stdio-common/vfprintf-internal.c
> index c76c06e49b..58c21481ce 100644
> --- a/stdio-common/vfprintf-internal.c
> +++ b/stdio-common/vfprintf-internal.c
> @@ -1001,6 +1001,7 @@ printf_positional (struct Xprintf_buffer * buf, const CHAR_T *format,
> scratch_buffer_init (&specsbuf);
> struct printf_spec *specs = specsbuf.data;
> size_t specs_limit = specsbuf.length / sizeof (specs[0]);
> + bool malloced_pa_user = false;
>
> /* Used as a backing store for args_value, args_size, args_type
> below. */
> @@ -1171,7 +1172,10 @@ printf_positional (struct Xprintf_buffer * buf, const CHAR_T *format,
> else if (__glibc_unlikely (__printf_va_arg_table != NULL)
> && __printf_va_arg_table[args_type[cnt] - PA_LAST] != NULL)
> {
> - args_value[cnt].pa_user = alloca (args_size[cnt]);
> + args_value[cnt].pa_user = malloc (args_size[cnt]);
> + if (args_value[cnt].pa_user == NULL)
> + break;
> + malloced_pa_user = true;
> (*__printf_va_arg_table[args_type[cnt] - PA_LAST])
> (args_value[cnt].pa_user, ap_savep);
> }
> @@ -1334,7 +1338,11 @@ printf_positional (struct Xprintf_buffer * buf, const CHAR_T *format,
> (specs[nspecs_done].next_fmt
> - specs[nspecs_done].end_of_fmt));
> }
> all_done:
> + if (malloced_pa_user)
> + for (cnt = 0; cnt < nargs; ++cnt)
> + free (args_value[cnt].pa_user);
> scratch_buffer_free (&argsbuf);
> scratch_buffer_free (&specsbuf);
> }
--
Cheers,
Carlos.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] vfprintf-internal: Replace alloca with malloc.
2023-05-15 18:35 ` Carlos O'Donell
@ 2023-05-15 18:49 ` Joe Simmons-Talbott
0 siblings, 0 replies; 3+ messages in thread
From: Joe Simmons-Talbott @ 2023-05-15 18:49 UTC (permalink / raw)
To: Carlos O'Donell; +Cc: libc-alpha
On Mon, May 15, 2023 at 02:35:36PM -0400, Carlos O'Donell wrote:
> On 5/10/23 11:32, Joe Simmons-Talbott via Libc-alpha wrote:
> > Avoid potential stack overflow from unbounded alloca.
>
> This fails to apply in pre-commit CI e.g. error: corrupt patch at line 145
>
> How did you generate this patch?
I used 'git format-patch' but then removed a blank line that the patch
added during 'git send-email --annotate'. Sorry. I'll post a v3
shortly.
Thanks,
Joe
^ permalink raw reply [flat|nested] 3+ messages in thread
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2023-05-10 15:32 [PATCH v2] vfprintf-internal: Replace alloca with malloc Joe Simmons-Talbott
2023-05-15 18:35 ` Carlos O'Donell
2023-05-15 18:49 ` Joe Simmons-Talbott
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