Re: [PATCH] kernel/bpf: htab_map_alloc() exit by free_map_locked logic issue
From: Stanislav Fomichev <hidden>
Date: 2022-09-10 20:30:07
Also in:
bpf, lkml
On Fri, Sep 9, 2022 at 7:07 PM [off-list ref] wrote:
From: eadivs <redacted> syzbot is reporting WARNING: ODEBUG bug in htab_map_alloc(), the loop exits without reaching length HASHTAB_MAP_LOCK_COUNT, and the loop continues HASHTAB_MAP_LOCK_COUNT times in label free_map_locked.
Please use [PATCH bpf] vs [PATCH bpf-next] in subject to indicate which tree you're targeting. Also, it seems your email hasn't reached the mailing list for some reason. Are you sure that the issue is due to HASHTAB_MAP_LOCK_COUNT? The code seems fine as is; unconditionally calling free on NULL shouldn't be an issue. htab_map_alloc+0xc76/0x1620 kernel/bpf/hashtab.c:632 Which, if I'm looking at the function is: bpf_map_area_free(htab); ?
quoted hunk
Link: https://syzkaller.appspot.com/bug?extid=5d1da78b375c3b5e6c2b Reported-by: syzbot+5d1da78b375c3b5e6c2b@syzkaller.appspotmail.com Signed-off-by: eadivs <redacted> --- kernel/bpf/hashtab.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 65877967f414..f5381e1c00a6 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c@@ -473,7 +473,7 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU); bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC); struct bpf_htab *htab; - int err, i; + int err, i, j = HASHTAB_MAP_LOCK_COUNT; htab = kzalloc(sizeof(*htab), GFP_USER | __GFP_ACCOUNT); if (!htab)@@ -523,8 +523,10 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) sizeof(int), sizeof(int), GFP_USER); - if (!htab->map_locked[i]) + if (!htab->map_locked[i]) { + j = i; goto free_map_locked; + } } if (htab->map.map_flags & BPF_F_ZERO_SEED)@@ -554,7 +556,7 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) free_prealloc: prealloc_destroy(htab); free_map_locked: - for (i = 0; i < HASHTAB_MAP_LOCK_COUNT; i++) + for (i = 0; i < j; i++) free_percpu(htab->map_locked[i]); bpf_map_area_free(htab->buckets); free_htab: --2.37.2