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Date: Thu, 24 Nov 2022 17:49:41 +0000 From: Srinivas Kandagatla <srinivas.kandagatla@...aro.org> To: gregkh@...uxfoundation.org Cc: linux-kernel@...r.kernel.org, Ola Jeppsson <ola@...p.com>, Abel Vesa <abel.vesa@...aro.org>, Srinivas Kandagatla <srinivas.kandagatla@...aro.org> Subject: [PATCH 3/3] misc: fastrpc: Fix use-after-free race condition for maps From: Ola Jeppsson <ola@...p.com> It is possible that in between calling fastrpc_map_get() until map->fl->lock is taken in fastrpc_free_map(), another thread can call fastrpc_map_lookup() and get a reference to a map that is about to be deleted. Rewrite fastrpc_map_get() to only increase the reference count of a map if it's non-zero. Propagate this to callers so they can know if a map is about to be deleted. Fixes this warning: refcount_t: addition on 0; use-after-free. WARNING: CPU: 5 PID: 10100 at lib/refcount.c:25 refcount_warn_saturate ... Call trace: refcount_warn_saturate [fastrpc_map_get inlined] [fastrpc_map_lookup inlined] fastrpc_map_create fastrpc_internal_invoke fastrpc_device_ioctl __arm64_sys_ioctl invoke_syscall Fixes: c68cfb718c8f ("misc: fastrpc: Add support for context Invoke method") Signed-off-by: Ola Jeppsson <ola@...p.com> Signed-off-by: Abel Vesa <abel.vesa@...aro.org> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org> --- drivers/misc/fastrpc.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c index 9ecbf673d321..80811e852d8f 100644 --- a/drivers/misc/fastrpc.c +++ b/drivers/misc/fastrpc.c @@ -332,10 +332,12 @@ static void fastrpc_map_put(struct fastrpc_map *map) kref_put(&map->refcount, fastrpc_free_map); } -static void fastrpc_map_get(struct fastrpc_map *map) +static int fastrpc_map_get(struct fastrpc_map *map) { - if (map) - kref_get(&map->refcount); + if (!map) + return -ENOENT; + + return kref_get_unless_zero(&map->refcount) ? 0 : -ENOENT; } -- 2.25.1
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