2022-09-02 15:54:34

by Abel Vesa

Subject: [PATCH 2/3] misc: fastrpc: Don't remove map on creater_process and device_release

Do not remove the map from the list on error path in
fastrpc_init_create_process, instead call fastrpc_map_put, to avoid
use-after-free. Do not remove it on fastrpc_device_release either,
call fastrpc_map_put instead.

The fastrpc_free_map is the only proper place to remove the map.
This is called only after the reference count is 0.

Fixes: b49f6d83e290f ("misc: fastrpc: Fix a possible double free")
Co-developed-by: Ola Jeppsson <[email protected]>
Signed-off-by: Ola Jeppsson <[email protected]>
Signed-off-by: Abel Vesa <[email protected]>
---
drivers/misc/fastrpc.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index 0c816a11eeec..50c17f5da3a8 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -316,6 +316,13 @@ static void fastrpc_free_map(struct kref *ref)
dma_buf_put(map->buf);
}

+ if (map->fl) {
+ spin_lock(&map->fl->lock);
+ list_del(&map->node);
+ spin_unlock(&map->fl->lock);
+ map->fl = NULL;
+ }
+
kfree(map);
}

@@ -1266,12 +1273,7 @@ static int fastrpc_init_create_process(struct fastrpc_user *fl,
fl->init_mem = NULL;
fastrpc_buf_free(imem);
err_alloc:
- if (map) {
- spin_lock(&fl->lock);
- list_del(&map->node);
- spin_unlock(&fl->lock);
- fastrpc_map_put(map);
- }
+ fastrpc_map_put(map);
err:
kfree(args);

@@ -1347,10 +1349,8 @@ static int fastrpc_device_release(struct inode *inode, struct file *file)
fastrpc_context_put(ctx);
}

- list_for_each_entry_safe(map, m, &fl->maps, node) {
- list_del(&map->node);
+ list_for_each_entry_safe(map, m, &fl->maps, node)
fastrpc_map_put(map);
- }

list_for_each_entry_safe(buf, b, &fl->mmaps, node) {
list_del(&buf->node);
--
2.34.1

2022-09-22 23:05:34

by Srinivas Kandagatla

Subject: Re: [PATCH 2/3] misc: fastrpc: Don't remove map on creater_process and device_release

On 02/09/2022 16:14, Abel Vesa wrote:
> Do not remove the map from the list on error path in
> fastrpc_init_create_process, instead call fastrpc_map_put, to avoid
> use-after-free. Do not remove it on fastrpc_device_release either,
> call fastrpc_map_put instead.
>
> The fastrpc_free_map is the only proper place to remove the map.
> This is called only after the reference count is 0.
>
> Fixes: b49f6d83e290f ("misc: fastrpc: Fix a possible double free")
> Co-developed-by: Ola Jeppsson <[email protected]>
> Signed-off-by: Ola Jeppsson <[email protected]>
> Signed-off-by: Abel Vesa <[email protected]>
> ---

Reviewed-by: Srinivas Kandagatla <[email protected]>

> drivers/misc/fastrpc.c | 18 +++++++++---------
> 1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index 0c816a11eeec..50c17f5da3a8 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -316,6 +316,13 @@ static void fastrpc_free_map(struct kref *ref)
> dma_buf_put(map->buf);
> }
>
> + if (map->fl) {
> + spin_lock(&map->fl->lock);
> + list_del(&map->node);
> + spin_unlock(&map->fl->lock);
> + map->fl = NULL;
> + }
> +
> kfree(map);
> }
>
> @@ -1266,12 +1273,7 @@ static int fastrpc_init_create_process(struct fastrpc_user *fl,
> fl->init_mem = NULL;
> fastrpc_buf_free(imem);
> err_alloc:
> - if (map) {
> - spin_lock(&fl->lock);
> - list_del(&map->node);
> - spin_unlock(&fl->lock);
> - fastrpc_map_put(map);
> - }
> + fastrpc_map_put(map);
> err:
> kfree(args);
>
> @@ -1347,10 +1349,8 @@ static int fastrpc_device_release(struct inode *inode, struct file *file)
> fastrpc_context_put(ctx);
> }
>
> - list_for_each_entry_safe(map, m, &fl->maps, node) {
> - list_del(&map->node);
> + list_for_each_entry_safe(map, m, &fl->maps, node)
> fastrpc_map_put(map);
> - }
>
> list_for_each_entry_safe(buf, b, &fl->mmaps, node) {
> list_del(&buf->node);