alpha: correct handling of negative *rlimit() args besides -1

Message ID 20221008024522.523048-1-mattst88@gmail.com
State Under Review
Headers
Series alpha: correct handling of negative *rlimit() args besides -1 |

Checks

Context Check Description
dj/TryBot-apply_patch success Patch applied to master at the time it was sent
dj/TryBot-32bit success Build for i686

Commit Message

Matt Turner Oct. 8, 2022, 2:45 a.m. UTC
  The generic version of RLIM_INFINITY in Linux is equal to (rlim_t)-1,
which is equal to ULLONG_MAX.  On alpha however it is instead defined as
0x7ffffffffffffffful.  This was special-cased in 0d0bc78 [BZ #22648] but
it specifically used an equality check.

There is a cpython test case test_prlimit_refcount which calls
setrlimit() with { -2, -2 } as arguments rather than the usual -1, it
therefore fails the equality test and is treated as a large arbitrary
positive value past the maximum of RLIM_INFINITY and fails with EPERM.
This patch changes the behavior of the *rlimit() calls to treat all
integers between 0x7ffffffffffffffful and (rlim_t)-1 as (rlim_t)-1,
i.e., RLIM_INFINITY.
---
 sysdeps/unix/sysv/linux/alpha/getrlimit64.c | 4 ++--
 sysdeps/unix/sysv/linux/alpha/setrlimit64.c | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)
  

Comments

Carlos O'Donell Oct. 10, 2022, 12:51 a.m. UTC | #1
On 10/7/22 22:45, Matt Turner via Libc-alpha wrote:
> The generic version of RLIM_INFINITY in Linux is equal to (rlim_t)-1,
> which is equal to ULLONG_MAX.  On alpha however it is instead defined as
> 0x7ffffffffffffffful.  This was special-cased in 0d0bc78 [BZ #22648] but
> it specifically used an equality check.
> 
> There is a cpython test case test_prlimit_refcount which calls
> setrlimit() with { -2, -2 } as arguments rather than the usual -1, it
> therefore fails the equality test and is treated as a large arbitrary
> positive value past the maximum of RLIM_INFINITY and fails with EPERM.
> This patch changes the behavior of the *rlimit() calls to treat all
> integers between 0x7ffffffffffffffful and (rlim_t)-1 as (rlim_t)-1,
> i.e., RLIM_INFINITY.
> ---
>  sysdeps/unix/sysv/linux/alpha/getrlimit64.c | 4 ++--
>  sysdeps/unix/sysv/linux/alpha/setrlimit64.c | 4 ++--

Is MIPS affected by the same problem?

>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/sysdeps/unix/sysv/linux/alpha/getrlimit64.c b/sysdeps/unix/sysv/linux/alpha/getrlimit64.c
> index c195f5b55c..40f3e6bdff 100644
> --- a/sysdeps/unix/sysv/linux/alpha/getrlimit64.c
> +++ b/sysdeps/unix/sysv/linux/alpha/getrlimit64.c
> @@ -38,11 +38,11 @@ __old_getrlimit64 (enum __rlimit_resource resource,
>    if (__getrlimit64 (resource, &krlimits) < 0)
>      return -1;
>  
> -  if (krlimits.rlim_cur == RLIM64_INFINITY)
> +  if (krlimits.rlim_cur >= OLD_RLIM64_INFINITY)
>      rlimits->rlim_cur = OLD_RLIM64_INFINITY;
>    else
>      rlimits->rlim_cur = krlimits.rlim_cur;
> -  if (krlimits.rlim_max == RLIM64_INFINITY)
> +  if (krlimits.rlim_max >= OLD_RLIM64_INFINITY)
>      rlimits->rlim_max = OLD_RLIM64_INFINITY;
>    else
>      rlimits->rlim_max = krlimits.rlim_max;
> diff --git a/sysdeps/unix/sysv/linux/alpha/setrlimit64.c b/sysdeps/unix/sysv/linux/alpha/setrlimit64.c
> index 421616ed20..4e88540a48 100644
> --- a/sysdeps/unix/sysv/linux/alpha/setrlimit64.c
> +++ b/sysdeps/unix/sysv/linux/alpha/setrlimit64.c
> @@ -35,11 +35,11 @@ __old_setrlimit64 (enum __rlimit_resource resource,
>  {
>    struct rlimit64 krlimits;
>  
> -  if (rlimits->rlim_cur == OLD_RLIM64_INFINITY)
> +  if (rlimits->rlim_cur >= OLD_RLIM64_INFINITY)
>      krlimits.rlim_cur = RLIM64_INFINITY;
>    else
>      krlimits.rlim_cur = rlimits->rlim_cur;
> -  if (rlimits->rlim_max == OLD_RLIM64_INFINITY)
> +  if (rlimits->rlim_max >= OLD_RLIM64_INFINITY)
>      krlimits.rlim_max = RLIM64_INFINITY;
>    else
>      krlimits.rlim_max = rlimits->rlim_max;
  
Matt Turner Oct. 10, 2022, 2:18 a.m. UTC | #2
On Sun, Oct 9, 2022 at 8:51 PM Carlos O'Donell <carlos@redhat.com> wrote:
>
> On 10/7/22 22:45, Matt Turner via Libc-alpha wrote:
> > The generic version of RLIM_INFINITY in Linux is equal to (rlim_t)-1,
> > which is equal to ULLONG_MAX.  On alpha however it is instead defined as
> > 0x7ffffffffffffffful.  This was special-cased in 0d0bc78 [BZ #22648] but
> > it specifically used an equality check.
> >
> > There is a cpython test case test_prlimit_refcount which calls
> > setrlimit() with { -2, -2 } as arguments rather than the usual -1, it
> > therefore fails the equality test and is treated as a large arbitrary
> > positive value past the maximum of RLIM_INFINITY and fails with EPERM.
> > This patch changes the behavior of the *rlimit() calls to treat all
> > integers between 0x7ffffffffffffffful and (rlim_t)-1 as (rlim_t)-1,
> > i.e., RLIM_INFINITY.
> > ---
> >  sysdeps/unix/sysv/linux/alpha/getrlimit64.c | 4 ++--
> >  sysdeps/unix/sysv/linux/alpha/setrlimit64.c | 4 ++--
>
> Is MIPS affected by the same problem?

Looks to me like it is, but I don't have a mips system running to
confirm. If this patch is accepted, I'll send a follow-up for mips.
  
Aurelien Jarno Oct. 10, 2022, 6:44 p.m. UTC | #3
Hi,

On 2022-10-07 22:45, Matt Turner via Libc-alpha wrote:
> The generic version of RLIM_INFINITY in Linux is equal to (rlim_t)-1,
> which is equal to ULLONG_MAX.  On alpha however it is instead defined as
> 0x7ffffffffffffffful.  This was special-cased in 0d0bc78 [BZ #22648] but
> it specifically used an equality check.

I am not sure this commit is giving the full picture, commits around
should also be checked to understand it.

> There is a cpython test case test_prlimit_refcount which calls
> setrlimit() with { -2, -2 } as arguments rather than the usual -1, it
> therefore fails the equality test and is treated as a large arbitrary
> positive value past the maximum of RLIM_INFINITY and fails with EPERM.
> This patch changes the behavior of the *rlimit() calls to treat all
> integers between 0x7ffffffffffffffful and (rlim_t)-1 as (rlim_t)-1,
> i.e., RLIM_INFINITY.
 
Basically on alpha, the glibc API is now identical to the prlimit64 API,
which means there is a dead zone with invalid values from
0x8000000000000000ul to 0xfffffffffffffffeul. The kernel returns EPERM
for values in this range.

You suggestion is to consider values is this zone as infinity. I have
mixed feeling about that. From the setrlimit() side it looks like the
correct thing to do. But this breaks the assumption that calling
getrlimit() after a successful setrlimit() call will return the same
value.

> diff --git a/sysdeps/unix/sysv/linux/alpha/getrlimit64.c b/sysdeps/unix/sysv/linux/alpha/getrlimit64.c
> index c195f5b55c..40f3e6bdff 100644
> --- a/sysdeps/unix/sysv/linux/alpha/getrlimit64.c
> +++ b/sysdeps/unix/sysv/linux/alpha/getrlimit64.c
> @@ -38,11 +38,11 @@ __old_getrlimit64 (enum __rlimit_resource resource,
>    if (__getrlimit64 (resource, &krlimits) < 0)
>      return -1;
>  
> -  if (krlimits.rlim_cur == RLIM64_INFINITY)
> +  if (krlimits.rlim_cur >= OLD_RLIM64_INFINITY)
>      rlimits->rlim_cur = OLD_RLIM64_INFINITY;
>    else
>      rlimits->rlim_cur = krlimits.rlim_cur;
> -  if (krlimits.rlim_max == RLIM64_INFINITY)
> +  if (krlimits.rlim_max >= OLD_RLIM64_INFINITY)
>      rlimits->rlim_max = OLD_RLIM64_INFINITY;
>    else
>      rlimits->rlim_max = krlimits.rlim_max;

That said, I do not understand the change there. It is done on the
*compat* symbol which still uses the old glibc API definition. There we
want to keep doing the exact reverse operations as in the
rlim_to_rlim64() kernel function.

> diff --git a/sysdeps/unix/sysv/linux/alpha/setrlimit64.c b/sysdeps/unix/sysv/linux/alpha/setrlimit64.c
> index 421616ed20..4e88540a48 100644
> --- a/sysdeps/unix/sysv/linux/alpha/setrlimit64.c
> +++ b/sysdeps/unix/sysv/linux/alpha/setrlimit64.c
> @@ -35,11 +35,11 @@ __old_setrlimit64 (enum __rlimit_resource resource,
>  {
>    struct rlimit64 krlimits;
>  
> -  if (rlimits->rlim_cur == OLD_RLIM64_INFINITY)
> +  if (rlimits->rlim_cur >= OLD_RLIM64_INFINITY)
>      krlimits.rlim_cur = RLIM64_INFINITY;
>    else
>      krlimits.rlim_cur = rlimits->rlim_cur;
> -  if (rlimits->rlim_max == OLD_RLIM64_INFINITY)
> +  if (rlimits->rlim_max >= OLD_RLIM64_INFINITY)
>      krlimits.rlim_max = RLIM64_INFINITY;
>    else
>      krlimits.rlim_max = rlimits->rlim_max;

Ditto here we want to do the reverse operations as the rlim64_to_rlim()
kernel function.
  

Patch

diff --git a/sysdeps/unix/sysv/linux/alpha/getrlimit64.c b/sysdeps/unix/sysv/linux/alpha/getrlimit64.c
index c195f5b55c..40f3e6bdff 100644
--- a/sysdeps/unix/sysv/linux/alpha/getrlimit64.c
+++ b/sysdeps/unix/sysv/linux/alpha/getrlimit64.c
@@ -38,11 +38,11 @@  __old_getrlimit64 (enum __rlimit_resource resource,
   if (__getrlimit64 (resource, &krlimits) < 0)
     return -1;
 
-  if (krlimits.rlim_cur == RLIM64_INFINITY)
+  if (krlimits.rlim_cur >= OLD_RLIM64_INFINITY)
     rlimits->rlim_cur = OLD_RLIM64_INFINITY;
   else
     rlimits->rlim_cur = krlimits.rlim_cur;
-  if (krlimits.rlim_max == RLIM64_INFINITY)
+  if (krlimits.rlim_max >= OLD_RLIM64_INFINITY)
     rlimits->rlim_max = OLD_RLIM64_INFINITY;
   else
     rlimits->rlim_max = krlimits.rlim_max;
diff --git a/sysdeps/unix/sysv/linux/alpha/setrlimit64.c b/sysdeps/unix/sysv/linux/alpha/setrlimit64.c
index 421616ed20..4e88540a48 100644
--- a/sysdeps/unix/sysv/linux/alpha/setrlimit64.c
+++ b/sysdeps/unix/sysv/linux/alpha/setrlimit64.c
@@ -35,11 +35,11 @@  __old_setrlimit64 (enum __rlimit_resource resource,
 {
   struct rlimit64 krlimits;
 
-  if (rlimits->rlim_cur == OLD_RLIM64_INFINITY)
+  if (rlimits->rlim_cur >= OLD_RLIM64_INFINITY)
     krlimits.rlim_cur = RLIM64_INFINITY;
   else
     krlimits.rlim_cur = rlimits->rlim_cur;
-  if (rlimits->rlim_max == OLD_RLIM64_INFINITY)
+  if (rlimits->rlim_max >= OLD_RLIM64_INFINITY)
     krlimits.rlim_max = RLIM64_INFINITY;
   else
     krlimits.rlim_max = rlimits->rlim_max;