GNU bug report logs - #77232
[PATCH] Allow also to get attributes of the terminal line

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Message #8 received at 77232 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Werner Fink <werner <at> suse.de>, Philipp Stephani <p.stephani2 <at> gmail.com>,
 Philipp Stephani <phst <at> google.com>
Cc: 77232 <at> debbugs.gnu.org
Subject: Re: bug#77232: [PATCH] Allow also to get attributes of the terminal
 line
Date: Mon, 24 Mar 2025 14:42:02 +0200

> Cc: Werner Fink <werner <at> suse.de>
> From: Werner Fink <werner <at> suse.de>
> Date: Mon, 24 Mar 2025 09:51:47 +0100
> 
> as well as support mmap(2) flag MAP_DROPPABLE to allow
> zero memory under memory pressure on newer Linux systems.
> 
> Otherwise a `make -k check` fails here in our build environment
> with newer kernels and with /dev/console as physical device.
> 
> Signed-off-by: Werner Fink <werner <at> suse.de>

Thanks.

Philipp, any comments?

> ---
>  lib-src/seccomp-filter.c | 19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git lib-src/seccomp-filter.c lib-src/seccomp-filter.c
> index d6421f0ebdb..4dda7d8f020 100644
> --- lib-src/seccomp-filter.c
> +++ lib-src/seccomp-filter.c
> @@ -42,6 +42,9 @@ variants of those files that can be used to sandbox Emacs before
>  #include <stdlib.h>
>  #include <stdint.h>
>  #include <stdio.h>
> +/* glibc uses internal an other TCGETS ioctl for its
> +   tcgetattr(3) call with its internal struct termios */
> +#include <asm/termbits.h>
>  #include <time.h>
>  
>  #include <asm/prctl.h>
> @@ -64,6 +67,11 @@ variants of those files that can be used to sandbox Emacs before
>  #define ARCH_CET_STATUS 0x3001
>  #endif
>  
> +/* https://github.com/torvalds/linux/commit/9651fcedf7b92d3f7f1ab179e8ab55b85ee10fc1 */
> +#ifndef MAP_DROPPABLE
> +#define MAP_DROPPABLE 0x0
> +#endif
> +
>  static ATTRIBUTE_FORMAT_PRINTF (2, 3) _Noreturn void
>  fail (int error, const char *format, ...)
>  {
> @@ -187,7 +195,7 @@ main (int argc, char **argv)
>             some versions of the dynamic loader still use it.  Also
>             allow allocating thread stacks.  */
>          SCMP_A3_32 (SCMP_CMP_MASKED_EQ,
> -                    ~(MAP_SHARED | MAP_PRIVATE | MAP_FILE
> +                    ~(MAP_SHARED | MAP_PRIVATE | MAP_FILE | MAP_DROPPABLE
>                        | MAP_ANONYMOUS | MAP_FIXED | MAP_DENYWRITE
>                        | MAP_STACK | MAP_NORESERVE),
>                      0));
> @@ -274,6 +282,11 @@ main (int argc, char **argv)
>          SCMP_A0_32 (SCMP_CMP_EQ, STDIN_FILENO),
>          SCMP_A1_32 (SCMP_CMP_EQ, TIOCGPGRP));
>  
> +  /* Allow `tcgetattr' call of glibc on physical terminal devices. */
> +  RULE (SCMP_ACT_ALLOW, SCMP_SYS (ioctl),
> +        SCMP_A0_32 (SCMP_CMP_EQ, STDERR_FILENO),
> +        SCMP_A1_32 (SCMP_CMP_EQ, TCGETS));
> +
>    /* Allow reading (but not setting) file flags.  */
>    RULE (SCMP_ACT_ALLOW, SCMP_SYS (fcntl),
>          SCMP_A1_32 (SCMP_CMP_EQ, F_GETFL));
> -- 
> 2.35.3
> 
> 
> 
> 
> 

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