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Fix seccomp-filter for newer Linux kernels

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* lib-src/seccomp-filter.c (MAP_DROPPABLE): Define if undefined.
(main): Use MAP_DROPPABLE flag.  Allow `tcgetattr' call of glibc
on physical terminal devices.  (Bug#77232)
This commit is contained in:
Werner Fink 2025-04-07 13:51:07 +02:00 • committed by Eli Zaretskii
parent 2cf545f47d
commit 8abd2ee052
1 changed files with 12 additions and 1 deletions
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13
lib-src/seccomp-filter.c
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@ -42,6 +42,7 @@ variants of those files that can be used to sandbox Emacs before
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <asm/termbits.h> /* mandatory accordingly to latest ioctl_tty(2) */
#include <time.h>
#include <asm/prctl.h>
@ -64,6 +65,11 @@ 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 0x08
#endif
static ATTRIBUTE_FORMAT_PRINTF (2, 3) _Noreturn void
fail (int error, const char *format, ...)
{
@ -187,7 +193,7 @@ 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 +280,11 @@ 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));