| Message ID | 20220902151423.3351414-1-abel.vesa@linaro.org |
|---|---|
| State | Superseded |
| 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: > Currently, there is a race window between the point when the mutex is > unlocked in fastrpc_map_lookup and the reference count increasing > (fastrpc_map_get) in fastrpc_map_find, which can also lead to > use-after-free. > > So lets merge fastrpc_map_find into fastrpc_map_lookup which allows us > to both protect the maps list by also taking the &fl->lock spinlock and > the reference count, since the spinlock will be released only after. > Add take_ref argument to make this suitable for all callers. > > Fixes: 8f6c1d8c4f0c ("misc: fastrpc: Add fdlist implementation") > Co-developed-by: Ola Jeppsson <ola@snap.com> > Signed-off-by: Ola Jeppsson <ola@snap.com> > Signed-off-by: Abel Vesa <abel.vesa@linaro.org> > --- Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> > drivers/misc/fastrpc.c | 41 +++++++++++++++++++++-------------------- > 1 file changed, 21 insertions(+), 20 deletions(-) > > diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c > index 93ebd174d848..0c816a11eeec 100644 > --- a/drivers/misc/fastrpc.c > +++ b/drivers/misc/fastrpc.c > @@ -333,30 +333,31 @@ static void fastrpc_map_get(struct fastrpc_map *map) > > > static int fastrpc_map_lookup(struct fastrpc_user *fl, int fd, > - struct fastrpc_map **ppmap) > + struct fastrpc_map **ppmap, bool take_ref) > { > + struct fastrpc_session_ctx *sess = fl->sctx; > struct fastrpc_map *map = NULL; > + int ret = -ENOENT; > > - mutex_lock(&fl->mutex); > + spin_lock(&fl->lock); > list_for_each_entry(map, &fl->maps, node) { > - if (map->fd == fd) { > - *ppmap = map; > - mutex_unlock(&fl->mutex); > - return 0; > - } > - } > - mutex_unlock(&fl->mutex); > - > - return -ENOENT; > -} > + if (map->fd != fd) > + continue; > > -static int fastrpc_map_find(struct fastrpc_user *fl, int fd, > - struct fastrpc_map **ppmap) > -{ > - int ret = fastrpc_map_lookup(fl, fd, ppmap); > + if (take_ref) { > + ret = fastrpc_map_get(map); > + if (ret) { > + dev_dbg(sess->dev, "%s: Failed to get map fd=%d ret=%d\n", > + __func__, fd, ret); > + break; > + } > + } > > - if (!ret) > - fastrpc_map_get(*ppmap); > + *ppmap = map; > + ret = 0; > + break; > + } > + spin_unlock(&fl->lock); > > return ret; > } > @@ -703,7 +704,7 @@ static int fastrpc_map_create(struct fastrpc_user *fl, int fd, > struct fastrpc_map *map = NULL; > int err = 0; > > - if (!fastrpc_map_find(fl, fd, ppmap)) > + if (!fastrpc_map_lookup(fl, fd, ppmap, true)) > return 0; > > map = kzalloc(sizeof(*map), GFP_KERNEL); > @@ -1026,7 +1027,7 @@ static int fastrpc_put_args(struct fastrpc_invoke_ctx *ctx, > for (i = 0; i < FASTRPC_MAX_FDLIST; i++) { > if (!fdlist[i]) > break; > - if (!fastrpc_map_lookup(fl, (int)fdlist[i], &mmap)) > + if (!fastrpc_map_lookup(fl, (int)fdlist[i], &mmap, false)) > fastrpc_map_put(mmap); > } >
diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c index 93ebd174d848..0c816a11eeec 100644 --- a/drivers/misc/fastrpc.c +++ b/drivers/misc/fastrpc.c @@ -333,30 +333,31 @@ static void fastrpc_map_get(struct fastrpc_map *map) static int fastrpc_map_lookup(struct fastrpc_user *fl, int fd, - struct fastrpc_map **ppmap) + struct fastrpc_map **ppmap, bool take_ref) { + struct fastrpc_session_ctx *sess = fl->sctx; struct fastrpc_map *map = NULL; + int ret = -ENOENT; - mutex_lock(&fl->mutex); + spin_lock(&fl->lock); list_for_each_entry(map, &fl->maps, node) { - if (map->fd == fd) { - *ppmap = map; - mutex_unlock(&fl->mutex); - return 0; - } - } - mutex_unlock(&fl->mutex); - - return -ENOENT; -} + if (map->fd != fd) + continue; -static int fastrpc_map_find(struct fastrpc_user *fl, int fd, - struct fastrpc_map **ppmap) -{ - int ret = fastrpc_map_lookup(fl, fd, ppmap); + if (take_ref) { + ret = fastrpc_map_get(map); + if (ret) { + dev_dbg(sess->dev, "%s: Failed to get map fd=%d ret=%d\n", + __func__, fd, ret); + break; + } + } - if (!ret) - fastrpc_map_get(*ppmap); + *ppmap = map; + ret = 0; + break; + } + spin_unlock(&fl->lock); return ret; } @@ -703,7 +704,7 @@ static int fastrpc_map_create(struct fastrpc_user *fl, int fd, struct fastrpc_map *map = NULL; int err = 0; - if (!fastrpc_map_find(fl, fd, ppmap)) + if (!fastrpc_map_lookup(fl, fd, ppmap, true)) return 0; map = kzalloc(sizeof(*map), GFP_KERNEL); @@ -1026,7 +1027,7 @@ static int fastrpc_put_args(struct fastrpc_invoke_ctx *ctx, for (i = 0; i < FASTRPC_MAX_FDLIST; i++) { if (!fdlist[i]) break; - if (!fastrpc_map_lookup(fl, (int)fdlist[i], &mmap)) + if (!fastrpc_map_lookup(fl, (int)fdlist[i], &mmap, false)) fastrpc_map_put(mmap); }
Currently, there is a race window between the point when the mutex is unlocked in fastrpc_map_lookup and the reference count increasing (fastrpc_map_get) in fastrpc_map_find, which can also lead to use-after-free. So lets merge fastrpc_map_find into fastrpc_map_lookup which allows us to both protect the maps list by also taking the &fl->lock spinlock and the reference count, since the spinlock will be released only after. Add take_ref argument to make this suitable for all callers. Fixes: 8f6c1d8c4f0c ("misc: fastrpc: Add fdlist implementation") Co-developed-by: Ola Jeppsson <ola@snap.com> Signed-off-by: Ola Jeppsson <ola@snap.com> Signed-off-by: Abel Vesa <abel.vesa@linaro.org> --- drivers/misc/fastrpc.c | 41 +++++++++++++++++++++-------------------- 1 file changed, 21 insertions(+), 20 deletions(-)