Messages in this thread | | | Date | Tue, 25 Jan 2022 09:26:21 +0800 | Subject | Re: [PATCH] bcache: Fix a NULL or wild pointer dereference in btree_gc_rewrite_node() | From | Coly Li <> |
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On 1/25/22 12:47 AM, Zhou Qingyang wrote: > In btree_gc_rewrite_node(), btree_node_alloc_replacement() is assigned to > n and return error code or NULL on failure. n is passed to > bch_btree_node_write_sync() and there is a dereference of it in > bch_btree_node_write_sync() without checks, which may lead to wild > pointer dereference or NULL pointer dereference depending on n. > > Fix this bug by adding IS_ERR_OR_NULL check of n. > > This bug was found by a static analyzer. > > Builds with 'make allyesconfig' show no new warnings, > and our static analyzer no longer warns about this code. > > Fixes: ("bcache: Rework btree cache reserve handling") > Signed-off-by: Zhou Qingyang <zhou1615@umn.edu> > --- > The analysis employs differential checking to identify inconsistent > security operations (e.g., checks or kfrees) between two code paths > and confirms that the inconsistent operations are not recovered in the > current function or the callers, so they constitute bugs. > > Note that, as a bug found by static analysis, it can be a false > positive or hard to trigger. Multiple researchers have cross-reviewed > the bug. > > drivers/md/bcache/btree.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c > index 88c573eeb598..06d42292e86c 100644 > --- a/drivers/md/bcache/btree.c > +++ b/drivers/md/bcache/btree.c > @@ -1504,6 +1504,8 @@ static int btree_gc_rewrite_node(struct btree *b, struct btree_op *op, > return 0; > > n = btree_node_alloc_replacement(replace, NULL); > + if (IS_ERR_OR_NULL(n)) > + return 0; >
Hi Qingyang,
This is a valid fix with my first glance. I add this patch into my testing queue.
Thanks.
Coly Li
> /* recheck reserve after allocating replacement node */ > if (btree_check_reserve(b, NULL)) {
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