[PATCH v2] malloc: Do not clobber errno on __getrandom_nocancel (BZ#29624)

[Yann Droneaud]

Hi,

29 septembre 2022 à 19:56 "Adhemerval Zanella via Libc-alpha" a écrit:

> 
> Use INTERNAL_SYSCALL_CALL instead of INLINE_SYSCALL_CALL. This
> requires emulate the semantic for hurd call (so __arc4random_buf
> uses the fallback).
> 
> Checked on x86_64-linux-gnu.
> ---
>  stdlib/arc4random.c | 4 ++--
>  sysdeps/mach/hurd/not-cancel.h | 12 ++++++++++--
>  sysdeps/unix/sysv/linux/not-cancel.h | 2 +-
>  3 files changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/stdlib/arc4random.c b/stdlib/arc4random.c
> index e417ef624d..0a1f4b8a57 100644
> --- a/stdlib/arc4random.c
> +++ b/stdlib/arc4random.c
> @@ -34,7 +34,7 @@ void
>  __arc4random_buf (void *p, size_t n)
>  {
>  static int seen_initialized;
> - size_t l;
> + int l;
>  int fd;
>  
>  if (n == 0)
> @@ -51,7 +51,7 @@ __arc4random_buf (void *p, size_t n)
>  n -= l;
>  continue; /* Interrupted by a signal; keep going. */
>  }
> - else if (l < 0 && errno == ENOSYS)

Aside: I failed to noticed this (the fact is, except commit message, I didn't review much Jason's patch) .

https://sourceware.org/pipermail/libc-alpha/2022-July/141049.html

l being size_t, it cannot be less than 0, thus is there a chance it can actually fallback to reading /dev/urandom ?

> + else if (l == -ENOSYS)
>  break; /* No syscall, so fallback to /dev/urandom. */
>  arc4random_getrandom_failure ();
>  }
> diff --git a/sysdeps/mach/hurd/not-cancel.h b/sysdeps/mach/hurd/not-cancel.h
> index ae58b734e3..518f738519 100644
> --- a/sysdeps/mach/hurd/not-cancel.h
> +++ b/sysdeps/mach/hurd/not-cancel.h
> @@ -27,6 +27,7 @@
>  #include <sys/uio.h>
>  #include <hurd.h>
>  #include <hurd/fd.h>
> +#include <sys/random.h>
>  
>  /* Non cancellable close syscall. */
>  __typeof (__close) __close_nocancel;
> @@ -75,8 +76,15 @@ __typeof (__fcntl) __fcntl_nocancel;
>  #define __fcntl64_nocancel(...) \
>  __fcntl_nocancel (__VA_ARGS__)
>  
> -#define __getrandom_nocancel(buf, size, flags) \
> - __getrandom (buf, size, flags)
> +static inline int
> +__getrandom_nocancel (void *buf, size_t buflen, unsigned int flags)
> +{
> + int save_errno = errno;
> + int r = __getrandom (buf, buflen, flags);
> + r = r == -1 ? -errno : r;
> + __set_errno (save_errno);
> + return r;
> +}
>  
>  #define __poll_infinity_nocancel(fds, nfds) \
>  __poll (fds, nfds, -1)
> diff --git a/sysdeps/unix/sysv/linux/not-cancel.h b/sysdeps/unix/sysv/linux/not-cancel.h
> index a263d294b1..00ab75a405 100644
> --- a/sysdeps/unix/sysv/linux/not-cancel.h
> +++ b/sysdeps/unix/sysv/linux/not-cancel.h
> @@ -71,7 +71,7 @@ __writev_nocancel_nostatus (int fd, const struct iovec *iov, int iovcnt)
>  static inline int
>  __getrandom_nocancel (void *buf, size_t buflen, unsigned int flags)
>  {
> - return INLINE_SYSCALL_CALL (getrandom, buf, buflen, flags);
> + return INTERNAL_SYSCALL_CALL (getrandom, buf, buflen, flags);
>  }
>  
>  static inline int
> -- 
> 2.34.1
>

Reviewed-by: Yann Droneaud <ydroneaud@opteya.com>

-- 
Yann Droneaud
OPTEYA