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misc: fastrpc: Fix use-after-free race condition for maps

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commit 96b328d119eca7563c1edcc4e1039a62e6370ecb upstream.

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")
Cc: stable <stable@kernel.org>
Signed-off-by: Ola Jeppsson <ola@snap.com>
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20221124174941.418450-4-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ola Jeppsson 2022-11-24 17:49:41 +00:00 committed by Greg Kroah-Hartman
parent 4b5c44e924
commit 556dfdb226
1 changed files with 5 additions and 3 deletions
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8
drivers/misc/fastrpc.c
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@ -234,10 +234,12 @@ 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;
}
static int fastrpc_map_find(struct fastrpc_user *fl, int fd,