Re: [PATCH] linux-user: fix O_NONBLOCK in signalfd4() and eventfd2() syscalls

[Laurent Vivier]

Le 10/02/2021 à 07:12, Helge Deller a écrit :
> On the hppa target userspace binaries may call signalfd4() and
> eventfd2() with an old TARGET_O_NONBLOCK value of 000200004 instead of
> 000200000 for the "mask" syscall parameter, in which case the current
> emulation doesn't handle the translation to the native O_NONBLOCK value
> correctly.
> 
> The 0x04 bit is not masked out before the new O_NONBLOCK bit is set and
> as such when calling the native syscall errors out with EINVAL.
> 
> Fix this by introducing TARGET_O_NONBLOCK_MASK which is used to mask off
> all possible bits. This define defaults to TARGET_O_NONBLOCK when not
> defined otherwise, so for all other targets the implementation will
> behave as before.
> 
> This patch needs to be applied on top of my previous two patches.
> 
> Bug was found and patch was verified by using qemu-hppa as debian buildd
> server on x86_64.
> 
> Signed-off-by: Helge Deller <deller@gmx.de>
> 
> ---
> 
> diff --git a/linux-user/hppa/target_fcntl.h b/linux-user/hppa/target_fcntl.h
> index 08e3a4fcb0..4eb0ec98e2 100644
> --- a/linux-user/hppa/target_fcntl.h
> +++ b/linux-user/hppa/target_fcntl.h
> @@ -9,6 +9,7 @@
>  #define HPPA_TARGET_FCNTL_H
> 
>  #define TARGET_O_NONBLOCK    000200000
> +#define TARGET_O_NONBLOCK_MASK 000200004 /* includes old HP-UX NDELAY flag */
>  #define TARGET_O_APPEND      000000010
>  #define TARGET_O_CREAT       000000400 /* not fcntl */
>  #define TARGET_O_EXCL        000002000 /* not fcntl */
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 27adee908e..3031aa342f 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -273,6 +273,11 @@ static type name (type1 arg1,type2 arg2,type3 arg3,type4 
> arg4,type5 arg5,        \
>  #define TARGET_NR__llseek TARGET_NR_llseek
>  #endif
> 
> +/* some platforms need to mask more bits than just TARGET_O_NONBLOCK */
> +#ifndef TARGET_O_NONBLOCK_MASK
> +#define TARGET_O_NONBLOCK_MASK TARGET_O_NONBLOCK
> +#endif
> +
>  #define __NR_sys_gettid __NR_gettid
>  _syscall0(int, sys_gettid)
> 
> @@ -7719,7 +7724,7 @@ static abi_long do_signalfd4(int fd, abi_long mask, int 
> flags)
>      sigset_t host_mask;
>      abi_long ret;
> 
> -    if (flags & ~(TARGET_O_NONBLOCK | TARGET_O_CLOEXEC)) {
> +    if (flags & ~(TARGET_O_NONBLOCK_MASK | TARGET_O_CLOEXEC)) {
>          return -TARGET_EINVAL;
>      }
>      if (!lock_user_struct(VERIFY_READ, target_mask, mask, 1)) {
> @@ -12508,7 +12513,7 @@ static abi_long do_syscall1(void *cpu_env, int num, 
> abi_long arg1,
>  #if defined(TARGET_NR_eventfd2)
>      case TARGET_NR_eventfd2:
>      {
> -        int host_flags = arg2 & (~(TARGET_O_NONBLOCK | TARGET_O_CLOEXEC));
> +        int host_flags = arg2 & (~(TARGET_O_NONBLOCK_MASK | 
> TARGET_O_CLOEXEC));
>          if (arg2 & TARGET_O_NONBLOCK) {
>              host_flags |= O_NONBLOCK;
>          }
> 

You might also update fcntl_flags_tbl[], the first column is the mask.

Thanks,
Laurent
-