* [PATCH] arc4random: fix getrandom fallback to /dev/urandom
@ 2024-04-03 16:55 Anthony Iliopoulos
2024-04-03 17:26 ` Adhemerval Zanella Netto
2024-04-03 17:35 ` Florian Weimer
0 siblings, 2 replies; 5+ messages in thread
From: Anthony Iliopoulos @ 2024-04-03 16:55 UTC (permalink / raw)
To: libc-alpha
arc4random_buf relies on the errno of getrandom_nocancel to fallback to
/dev/urandom, but getrandom_nocancel returns a status code instead of
the syscall errno (-ENOSYS) so it breaks the expectation and thus the
fallback in cases where a kernel does not support the getrandom syscall.
Commit 609c9d0951da ("malloc: Do not clobber errno on __getrandom_nocancel
(BZ #29624)") changed __getrandom_nocancel from INLINE_SYSCALL_CALL to
INTERNAL_SYSCALL_CALL and modified arc4random_buf to rely on the return
status instead of errno.
Commit 5a85786a9005 ("Make __getrandom_nocancel set errno and add a
_nostatus version") changed __getrandom_nocancel back to
INLINE_SYSCALL_CALL and added a __getrandom_nocancel_nostatus variant
that calls via INTERNAL_SYSCALL_CALL, but this broke the fallback of
arc4random on kernels where the getrandom syscall is not available.
Fix it by calling __getrandom_nocancel_nostatus from arc4random_buf so
that the fallback works again.
Signed-off-by: Anthony Iliopoulos <ailiop@suse.com>
Fixes: 5a85786a9005 ("Make __getrandom_nocancel set errno and add a _nostatus version")
---
stdlib/arc4random.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/stdlib/arc4random.c b/stdlib/arc4random.c
index 3ae8fc130234..9b6a6ee85150 100644
--- a/stdlib/arc4random.c
+++ b/stdlib/arc4random.c
@@ -42,7 +42,7 @@ __arc4random_buf (void *p, size_t n)
for (;;)
{
- l = TEMP_FAILURE_RETRY (__getrandom_nocancel (p, n, 0));
+ l = TEMP_FAILURE_RETRY (__getrandom_nocancel_nostatus (p, n, 0));
if (l > 0)
{
if ((size_t) l == n)
--
2.44.0
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] arc4random: fix getrandom fallback to /dev/urandom
2024-04-03 16:55 [PATCH] arc4random: fix getrandom fallback to /dev/urandom Anthony Iliopoulos
@ 2024-04-03 17:26 ` Adhemerval Zanella Netto
2024-04-03 17:35 ` Florian Weimer
1 sibling, 0 replies; 5+ messages in thread
From: Adhemerval Zanella Netto @ 2024-04-03 17:26 UTC (permalink / raw)
To: Anthony Iliopoulos, libc-alpha
On 03/04/24 13:55, Anthony Iliopoulos wrote:
> arc4random_buf relies on the errno of getrandom_nocancel to fallback to
> /dev/urandom, but getrandom_nocancel returns a status code instead of
> the syscall errno (-ENOSYS) so it breaks the expectation and thus the
> fallback in cases where a kernel does not support the getrandom syscall.
>
> Commit 609c9d0951da ("malloc: Do not clobber errno on __getrandom_nocancel
> (BZ #29624)") changed __getrandom_nocancel from INLINE_SYSCALL_CALL to
> INTERNAL_SYSCALL_CALL and modified arc4random_buf to rely on the return
> status instead of errno.
>
> Commit 5a85786a9005 ("Make __getrandom_nocancel set errno and add a
> _nostatus version") changed __getrandom_nocancel back to
> INLINE_SYSCALL_CALL and added a __getrandom_nocancel_nostatus variant
> that calls via INTERNAL_SYSCALL_CALL, but this broke the fallback of
> arc4random on kernels where the getrandom syscall is not available.
>
> Fix it by calling __getrandom_nocancel_nostatus from arc4random_buf so
> that the fallback works again.
>
> Signed-off-by: Anthony Iliopoulos <ailiop@suse.com>
> Fixes: 5a85786a9005 ("Make __getrandom_nocancel set errno and add a _nostatus version")
It is a user-visible change, could you open a bug report so we can backport it
2.39? The patch looks good to me.
> ---
> stdlib/arc4random.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/stdlib/arc4random.c b/stdlib/arc4random.c
> index 3ae8fc130234..9b6a6ee85150 100644
> --- a/stdlib/arc4random.c
> +++ b/stdlib/arc4random.c
> @@ -42,7 +42,7 @@ __arc4random_buf (void *p, size_t n)
>
> for (;;)
> {
> - l = TEMP_FAILURE_RETRY (__getrandom_nocancel (p, n, 0));
> + l = TEMP_FAILURE_RETRY (__getrandom_nocancel_nostatus (p, n, 0));
> if (l > 0)
> {
> if ((size_t) l == n)
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] arc4random: fix getrandom fallback to /dev/urandom
2024-04-03 16:55 [PATCH] arc4random: fix getrandom fallback to /dev/urandom Anthony Iliopoulos
2024-04-03 17:26 ` Adhemerval Zanella Netto
@ 2024-04-03 17:35 ` Florian Weimer
2024-04-03 17:48 ` Adhemerval Zanella Netto
1 sibling, 1 reply; 5+ messages in thread
From: Florian Weimer @ 2024-04-03 17:35 UTC (permalink / raw)
To: Anthony Iliopoulos; +Cc: libc-alpha
* Anthony Iliopoulos:
> diff --git a/stdlib/arc4random.c b/stdlib/arc4random.c
> index 3ae8fc130234..9b6a6ee85150 100644
> --- a/stdlib/arc4random.c
> +++ b/stdlib/arc4random.c
> @@ -42,7 +42,7 @@ __arc4random_buf (void *p, size_t n)
>
> for (;;)
> {
> - l = TEMP_FAILURE_RETRY (__getrandom_nocancel (p, n, 0));
> + l = TEMP_FAILURE_RETRY (__getrandom_nocancel_nostatus (p, n, 0));
> if (l > 0)
> {
> if ((size_t) l == n)
TEMP_FAILURE_RETRY is incompatible with __getrandom_nocancel_nostatus.
You need to check for -EINTR and try again.
Thanks,
Florian
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] arc4random: fix getrandom fallback to /dev/urandom
2024-04-03 17:35 ` Florian Weimer
@ 2024-04-03 17:48 ` Adhemerval Zanella Netto
2024-04-03 17:50 ` Adhemerval Zanella Netto
0 siblings, 1 reply; 5+ messages in thread
From: Adhemerval Zanella Netto @ 2024-04-03 17:48 UTC (permalink / raw)
To: libc-alpha
On 03/04/24 14:35, Florian Weimer wrote:
> * Anthony Iliopoulos:
>
>> diff --git a/stdlib/arc4random.c b/stdlib/arc4random.c
>> index 3ae8fc130234..9b6a6ee85150 100644
>> --- a/stdlib/arc4random.c
>> +++ b/stdlib/arc4random.c
>> @@ -42,7 +42,7 @@ __arc4random_buf (void *p, size_t n)
>>
>> for (;;)
>> {
>> - l = TEMP_FAILURE_RETRY (__getrandom_nocancel (p, n, 0));
>> + l = TEMP_FAILURE_RETRY (__getrandom_nocancel_nostatus (p, n, 0));
>> if (l > 0)
>> {
>> if ((size_t) l == n)
>
> TEMP_FAILURE_RETRY is incompatible with __getrandom_nocancel_nostatus.
> You need to check for -EINTR and try again.
It does work, it will return -ENOSYS in this case.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] arc4random: fix getrandom fallback to /dev/urandom
2024-04-03 17:48 ` Adhemerval Zanella Netto
@ 2024-04-03 17:50 ` Adhemerval Zanella Netto
0 siblings, 0 replies; 5+ messages in thread
From: Adhemerval Zanella Netto @ 2024-04-03 17:50 UTC (permalink / raw)
To: libc-alpha
On 03/04/24 14:48, Adhemerval Zanella Netto wrote:
>
>
> On 03/04/24 14:35, Florian Weimer wrote:
>> * Anthony Iliopoulos:
>>
>>> diff --git a/stdlib/arc4random.c b/stdlib/arc4random.c
>>> index 3ae8fc130234..9b6a6ee85150 100644
>>> --- a/stdlib/arc4random.c
>>> +++ b/stdlib/arc4random.c
>>> @@ -42,7 +42,7 @@ __arc4random_buf (void *p, size_t n)
>>>
>>> for (;;)
>>> {
>>> - l = TEMP_FAILURE_RETRY (__getrandom_nocancel (p, n, 0));
>>> + l = TEMP_FAILURE_RETRY (__getrandom_nocancel_nostatus (p, n, 0));
>>> if (l > 0)
>>> {
>>> if ((size_t) l == n)
>>
>> TEMP_FAILURE_RETRY is incompatible with __getrandom_nocancel_nostatus.
>> You need to check for -EINTR and try again.
>
> It does work, it will return -ENOSYS in this case.
Right, it is need to handle the signal.
^ permalink raw reply [flat|nested] 5+ messages in thread
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2024-04-03 16:55 [PATCH] arc4random: fix getrandom fallback to /dev/urandom Anthony Iliopoulos
2024-04-03 17:26 ` Adhemerval Zanella Netto
2024-04-03 17:35 ` Florian Weimer
2024-04-03 17:48 ` Adhemerval Zanella Netto
2024-04-03 17:50 ` Adhemerval Zanella Netto
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