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bpf: Use refcount_t instead of atomic_t for mmap_count

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[ Upstream commit dfa94ce54f4139c893b9c4ec17df6f7c6a7515d3 ]

Use an API that resembles more the actual use of mmap_count.

Found by cocci:
kernel/bpf/arena.c:245:6-25: WARNING: atomic_dec_and_test variation before object free at line 249.

Fixes: b90d77e5fd ("bpf: Fix remap of arena.")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202412292037.LXlYSHKl-lkp@intel.com/
Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
Link: https://lore.kernel.org/r/6ecce439a6bc81adb85d5080908ea8959b792a50.1735542814.git.xiaopei01@kylinos.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Pei Xiao
2024-12-30 15:16:55 +08:00
committed by Greg Kroah-Hartman
parent e665c1f294
commit 8e7d29b698
1 changed files with 4 additions and 4 deletions
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8
kernel/bpf/arena.c
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@@ -212,7 +212,7 @@ static u64 arena_map_mem_usage(const struct bpf_map *map)
struct vma_list {
struct vm_area_struct *vma;
struct list_head head;
atomic_t mmap_count;
refcount_t mmap_count;
};
static int remember_vma(struct bpf_arena *arena, struct vm_area_struct *vma)
@@ -222,7 +222,7 @@ static int remember_vma(struct bpf_arena *arena, struct vm_area_struct *vma)
vml = kmalloc(sizeof(*vml), GFP_KERNEL);
if (!vml)
return -ENOMEM;
atomic_set(&vml->mmap_count, 1);
refcount_set(&vml->mmap_count, 1);
vma->vm_private_data = vml;
vml->vma = vma;
list_add(&vml->head, &arena->vma_list);
@@ -233,7 +233,7 @@ static void arena_vm_open(struct vm_area_struct *vma)
{
struct vma_list *vml = vma->vm_private_data;
atomic_inc(&vml->mmap_count);
refcount_inc(&vml->mmap_count);
}
static void arena_vm_close(struct vm_area_struct *vma)
@@ -242,7 +242,7 @@ static void arena_vm_close(struct vm_area_struct *vma)
struct bpf_arena *arena = container_of(map, struct bpf_arena, map);
struct vma_list *vml = vma->vm_private_data;
if (!atomic_dec_and_test(&vml->mmap_count))
if (!refcount_dec_and_test(&vml->mmap_count))
return;
guard(mutex)(&arena->lock);
/* update link list under lock */