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shm: fix segfault when accessing destroyed pool resource

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With wl_shm_buffer_ref_pool(), it's possible for a wl_shm_pool
to outlive its wl_resource. We need to be careful not to access
wl_shm_pool.resource if it's been destroyed.

Reset resource to NULL in the resource destroy handler, and add
NULL checks.

Signed-off-by: Simon Ser <contact@emersion.fr>
This commit is contained in:
Simon Ser 2022-09-16 09:53:39 +02:00
parent 6cdeae1bec
commit ab526f8d7c
1 changed files with 6 additions and 4 deletions
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10
src/wayland-shm.c
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@ -109,7 +109,7 @@ shm_pool_grow_mapping(struct wl_shm_pool *pool)
data = wl_os_mremap_maymove(pool->mmap_fd, pool->data, &pool->size, data = wl_os_mremap_maymove(pool->mmap_fd, pool->data, &pool->size,
pool->new_size, pool->mmap_prot, pool->new_size, pool->mmap_prot,
pool->mmap_flags); pool->mmap_flags);
if (pool->size != 0) { if (pool->size != 0 && pool->resource != NULL) {
wl_resource_post_error(pool->resource, wl_resource_post_error(pool->resource,
WL_SHM_ERROR_INVALID_FD, WL_SHM_ERROR_INVALID_FD,
"leaked old mapping"); "leaked old mapping");
@ -128,9 +128,10 @@ shm_pool_finish_resize(struct wl_shm_pool *pool)
data = shm_pool_grow_mapping(pool); data = shm_pool_grow_mapping(pool);
if (data == MAP_FAILED) { if (data == MAP_FAILED) {
wl_resource_post_error(pool->resource, if (pool->resource != NULL)
WL_SHM_ERROR_INVALID_FD, wl_resource_post_error(pool->resource,
"failed mremap"); WL_SHM_ERROR_INVALID_FD,
"failed mremap");
return; return;
} }
@ -260,6 +261,7 @@ destroy_pool(struct wl_resource *resource)
{ {
struct wl_shm_pool *pool = wl_resource_get_user_data(resource); struct wl_shm_pool *pool = wl_resource_get_user_data(resource);
pool->resource = NULL;
shm_pool_unref(pool, false); shm_pool_unref(pool, false);
} }