Hi Greg,
Here are 3 fixes that were discovered during product stress testing, fixes are
around a race condtion resulting in use after free which are fixed with
using correct locking.
Am really not sure if you are taking fixes late in this cycle.
In case you are not could you please apply them for 6.2
Thanks,
Srini
Abel Vesa (2):
misc: fastrpc: Fix use-after-free and race in fastrpc_map_find
misc: fastrpc: Don't remove map on creater_process and device_release
Ola Jeppsson (1):
misc: fastrpc: Fix use-after-free race condition for maps
drivers/misc/fastrpc.c | 67 ++++++++++++++++++++++--------------------
1 file changed, 35 insertions(+), 32 deletions(-)
--
2.25.1
From: Abel Vesa <[email protected]>
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 <[email protected]>
Signed-off-by: Ola Jeppsson <[email protected]>
Signed-off-by: Abel Vesa <[email protected]>
Signed-off-by: Srinivas Kandagatla <[email protected]>
---
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 7ff0b63c25e3..fc2173c59f8b 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);
}
--
2.25.1
From: Ola Jeppsson <[email protected]>
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 <[email protected]>
Signed-off-by: Abel Vesa <[email protected]>
Signed-off-by: Srinivas Kandagatla <[email protected]>
---
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