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bar: wayland: shm: try with MFD_NOEXEC_SEAL first, then without

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MFD_NOEXEC_SEAL is only supported on kernels 6.3 and later.

If we were compiled on linux >= 6.3, but run on linux < 6.3, we'd exit
with an error, due to memfd_create() failing with EINVAL.

This patch fixes the problem by first trying to call
memfd_create() *with* MFD_NOEXEC_SEAL, and if that fails with EINVAL,
we try again without it.
This commit is contained in:
Daniel Eklöf 2023-10-13 16:34:02 +02:00
parent cbd3bebb04
commit 89e74139f5
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GPG key ID: 5BBD4992C116573F
1 changed files with 15 additions and 5 deletions
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20
bar/wayland.c
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@ -28,10 +28,8 @@
#include "private.h"
#if defined(MFD_NOEXEC_SEAL)
#define YAMBAR_MFD_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_NOEXEC_SEAL)
#else
#define YAMBAR_MFD_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING)
#if !defined(MFD_NOEXEC_SEAL)
#define MFD_NOEXEC_SEAL 0
#endif
struct buffer {
@ -913,7 +911,19 @@ get_buffer(struct wayland_backend *backend)
/* Backing memory for SHM */
#if defined(MEMFD_CREATE)
pool_fd = memfd_create("yambar-wayland-shm-buffer-pool", YAMBAR_MFD_FLAGS);
/*
* Older kernels reject MFD_NOEXEC_SEAL with EINVAL. Try first
* *with* it, and if that fails, try again *without* it.
*/
errno = 0;
pool_fd = memfd_create(
"yambar-wayland-shm-buffer-pool",
MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_NOEXEC_SEAL);
if (pool_fd < 0 && errno == EINVAL) {
pool_fd = memfd_create(
"yambar-wayland-shm-buffer-pool", MFD_CLOEXEC | MFD_ALLOW_SEALING);
}
#elif defined(__FreeBSD__)
// memfd_create on FreeBSD 13 is SHM_ANON without sealing support
pool_fd = shm_open(SHM_ANON, O_RDWR | O_CLOEXEC, 0600);