| Message ID | 20220902151423.3351414-3-abel.vesa@linaro.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | [1/3] misc: fastrpc: Fix use-after-free and race in fastrpc_map_find | expand |
On 02/09/2022 16:14, Abel Vesa wrote: > From: Ola Jeppsson <ola@snap.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. > yes, there is a margin of window here. Also am surprised to see the race for same map fd. fastrpc_map_get() is always under a lock, have you tried adding locking for fastrpc_map_put(). > 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. This will work but it would be better to fix the window of race. --srini > > 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: c68cfb718c8f9 ("misc: fastrpc: Add support for context Invoke method") > Signed-off-by: Ola Jeppsson <ola@snap.com> > Signed-off-by: Abel Vesa <abel.vesa@linaro.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 50c17f5da3a8..58654d394d17 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; > } > >
diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c index 50c17f5da3a8..58654d394d17 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; }