getaddrinfo: Get rid of alloca
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Commit Message
Use a scratch_buffer rather than alloca to avoid potential stack
overflow.
---
sysdeps/posix/getaddrinfo.c | 22 ++++++++--------------
1 file changed, 8 insertions(+), 14 deletions(-)
Comments
On 20/06/23 18:40, Joe Simmons-Talbott via Libc-alpha wrote:
> Use a scratch_buffer rather than alloca to avoid potential stack
> overflow.
> ---
> sysdeps/posix/getaddrinfo.c | 22 ++++++++--------------
> 1 file changed, 8 insertions(+), 14 deletions(-)
>
> diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
> index 0356b622be..442475d621 100644
> --- a/sysdeps/posix/getaddrinfo.c
> +++ b/sysdeps/posix/getaddrinfo.c
> @@ -2404,22 +2404,17 @@ getaddrinfo (const char *name, const char *service,
> struct addrinfo *q;
> struct addrinfo *last = NULL;
> char *canonname = NULL;
> - bool malloc_results;
> size_t alloc_size = nresults * (sizeof (*results) + sizeof (size_t));
> + struct scratch_buffer buf;
> + scratch_buffer_init (&buf);
>
> - malloc_results
> - = !__libc_use_alloca (alloc_size);
> - if (malloc_results)
> + if (!scratch_buffer_set_array_size (&buf, 1, alloc_size))
I think it would be better to use:
if (!scratch_buffer_set_array_size (&buf, nresults,
sizeof (*results) + sizeof (size_t)))
[...]
To use the overflow checks done by scratch_buffer_set_array_size (
sizeof (*results) + sizeof (size_t) is always safe so I think there is no
need to add extra checks).
> {
> - results = malloc (alloc_size);
> - if (results == NULL)
> - {
> - __free_in6ai (in6ai);
> - return EAI_MEMORY;
> - }
> + __free_in6ai (in6ai);
> + return EAI_MEMORY;
> }
> - else
> - results = alloca (alloc_size);
> + results = buf.data;
> +
> order = (size_t *) (results + nresults);
>
> /* Now we definitely need the interface information. */
> @@ -2590,8 +2585,7 @@ getaddrinfo (const char *name, const char *service,
> /* Fill in the canonical name into the new first entry. */
> p->ai_canonname = canonname;
>
> - if (malloc_results)
> - free (results);
> + scratch_buffer_free (&buf);
> }
>
> __free_in6ai (in6ai);
On Fri, Jun 30, 2023 at 10:15:48AM -0300, Adhemerval Zanella Netto wrote:
>
>
> On 20/06/23 18:40, Joe Simmons-Talbott via Libc-alpha wrote:
> > Use a scratch_buffer rather than alloca to avoid potential stack
> > overflow.
> > ---
> > sysdeps/posix/getaddrinfo.c | 22 ++++++++--------------
> > 1 file changed, 8 insertions(+), 14 deletions(-)
> >
> > diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
> > index 0356b622be..442475d621 100644
> > --- a/sysdeps/posix/getaddrinfo.c
> > +++ b/sysdeps/posix/getaddrinfo.c
> > @@ -2404,22 +2404,17 @@ getaddrinfo (const char *name, const char *service,
> > struct addrinfo *q;
> > struct addrinfo *last = NULL;
> > char *canonname = NULL;
> > - bool malloc_results;
> > size_t alloc_size = nresults * (sizeof (*results) + sizeof (size_t));
> > + struct scratch_buffer buf;
> > + scratch_buffer_init (&buf);
> >
> > - malloc_results
> > - = !__libc_use_alloca (alloc_size);
> > - if (malloc_results)
> > + if (!scratch_buffer_set_array_size (&buf, 1, alloc_size))
>
> I think it would be better to use:
>
> if (!scratch_buffer_set_array_size (&buf, nresults,
> sizeof (*results) + sizeof (size_t)))
> [...]
>
> To use the overflow checks done by scratch_buffer_set_array_size (
> sizeof (*results) + sizeof (size_t) is always safe so I think there is no
> need to add extra checks).
You are correct. Thanks for catching that and for the review. I've
pushed your suggestion as v2.
Thanks,
Joe
@@ -2404,22 +2404,17 @@ getaddrinfo (const char *name, const char *service,
struct addrinfo *q;
struct addrinfo *last = NULL;
char *canonname = NULL;
- bool malloc_results;
size_t alloc_size = nresults * (sizeof (*results) + sizeof (size_t));
+ struct scratch_buffer buf;
+ scratch_buffer_init (&buf);
- malloc_results
- = !__libc_use_alloca (alloc_size);
- if (malloc_results)
+ if (!scratch_buffer_set_array_size (&buf, 1, alloc_size))
{
- results = malloc (alloc_size);
- if (results == NULL)
- {
- __free_in6ai (in6ai);
- return EAI_MEMORY;
- }
+ __free_in6ai (in6ai);
+ return EAI_MEMORY;
}
- else
- results = alloca (alloc_size);
+ results = buf.data;
+
order = (size_t *) (results + nresults);
/* Now we definitely need the interface information. */
@@ -2590,8 +2585,7 @@ getaddrinfo (const char *name, const char *service,
/* Fill in the canonical name into the new first entry. */
p->ai_canonname = canonname;
- if (malloc_results)
- free (results);
+ scratch_buffer_free (&buf);
}
__free_in6ai (in6ai);