2022-03-28 11:27:38

by Xiaomeng Tong

Subject: [PATCH] misc: fastrpc: fix an incorrect NULL check on list iterator

The bug is here:
if (!buf) {

The list iterator value 'buf' will *always* be set and non-NULL
by list_for_each_entry(), so it is incorrect to assume that the
iterator value will be NULL if the list is empty (in this case, the
check 'if (!buf) {' will always be false and never exit expectly).

To fix the bug, use a new variable 'iter' as the list iterator,
while use the original variable 'buf' as a dedicated pointer to
point to the found element.

Cc: [email protected]
Fixes: 2419e55e532de ("misc: fastrpc: add mmap/unmap support")
Signed-off-by: Xiaomeng Tong <[email protected]>
---
drivers/misc/fastrpc.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index aa1682b94a23..45aaf54a7560 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -1353,17 +1353,18 @@ static int fastrpc_req_munmap_impl(struct fastrpc_user *fl,
struct fastrpc_req_munmap *req)
{
struct fastrpc_invoke_args args[1] = { [0] = { 0 } };
- struct fastrpc_buf *buf, *b;
+ struct fastrpc_buf *buf = NULL, *iter, *b;
struct fastrpc_munmap_req_msg req_msg;
struct device *dev = fl->sctx->dev;
int err;
u32 sc;

spin_lock(&fl->lock);
- list_for_each_entry_safe(buf, b, &fl->mmaps, node) {
- if ((buf->raddr == req->vaddrout) && (buf->size == req->size))
+ list_for_each_entry_safe(iter, b, &fl->mmaps, node) {
+ if ((iter->raddr == req->vaddrout) && (iter->size == req->size)) {
+ buf = iter;
break;
- buf = NULL;
+ }
}
spin_unlock(&fl->lock);

--
2.17.1

2022-03-28 21:37:36

by Jorge Ramirez-Ortiz, Gmail

Subject: Re: [PATCH] misc: fastrpc: fix an incorrect NULL check on list iterator

On 27/03/22, Xiaomeng Tong wrote:
> The bug is here:
> if (!buf) {
>
> The list iterator value 'buf' will *always* be set and non-NULL
> by list_for_each_entry(), so it is incorrect to assume that the
> iterator value will be NULL if the list is empty (in this case, the
> check 'if (!buf) {' will always be false and never exit expectly).

yes.

>
> To fix the bug, use a new variable 'iter' as the list iterator,
> while use the original variable 'buf' as a dedicated pointer to
> point to the found element.

LGTM

>
> Cc: [email protected]
> Fixes: 2419e55e532de ("misc: fastrpc: add mmap/unmap support")
> Signed-off-by: Xiaomeng Tong <[email protected]>
> ---
> drivers/misc/fastrpc.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index aa1682b94a23..45aaf54a7560 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -1353,17 +1353,18 @@ static int fastrpc_req_munmap_impl(struct fastrpc_user *fl,
> struct fastrpc_req_munmap *req)
> {
> struct fastrpc_invoke_args args[1] = { [0] = { 0 } };
> - struct fastrpc_buf *buf, *b;
> + struct fastrpc_buf *buf = NULL, *iter, *b;
> struct fastrpc_munmap_req_msg req_msg;
> struct device *dev = fl->sctx->dev;
> int err;
> u32 sc;
>
> spin_lock(&fl->lock);
> - list_for_each_entry_safe(buf, b, &fl->mmaps, node) {
> - if ((buf->raddr == req->vaddrout) && (buf->size == req->size))
> + list_for_each_entry_safe(iter, b, &fl->mmaps, node) {
> + if ((iter->raddr == req->vaddrout) && (iter->size == req->size)) {
> + buf = iter;
> break;
> - buf = NULL;
> + }
> }
> spin_unlock(&fl->lock);
>
> --
> 2.17.1
>

2022-04-29 19:59:06

by Srinivas Kandagatla

Subject: Re: [PATCH] misc: fastrpc: fix an incorrect NULL check on list iterator

On 27/03/2022 07:22, Xiaomeng Tong wrote:
> The bug is here:
> if (!buf) {
>
> The list iterator value 'buf' will *always* be set and non-NULL
> by list_for_each_entry(), so it is incorrect to assume that the
> iterator value will be NULL if the list is empty (in this case, the
> check 'if (!buf) {' will always be false and never exit expectly).
>
> To fix the bug, use a new variable 'iter' as the list iterator,
> while use the original variable 'buf' as a dedicated pointer to
> point to the found element.
>
> Cc: [email protected]
> Fixes: 2419e55e532de ("misc: fastrpc: add mmap/unmap support")
> Signed-off-by: Xiaomeng Tong <[email protected]>
LGTM,

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

> --- > drivers/misc/fastrpc.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index aa1682b94a23..45aaf54a7560 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -1353,17 +1353,18 @@ static int fastrpc_req_munmap_impl(struct fastrpc_user *fl,
> struct fastrpc_req_munmap *req)
> {
> struct fastrpc_invoke_args args[1] = { [0] = { 0 } };
> - struct fastrpc_buf *buf, *b;
> + struct fastrpc_buf *buf = NULL, *iter, *b;
> struct fastrpc_munmap_req_msg req_msg;
> struct device *dev = fl->sctx->dev;
> int err;
> u32 sc;
>
> spin_lock(&fl->lock);
> - list_for_each_entry_safe(buf, b, &fl->mmaps, node) {
> - if ((buf->raddr == req->vaddrout) && (buf->size == req->size))
> + list_for_each_entry_safe(iter, b, &fl->mmaps, node) {
> + if ((iter->raddr == req->vaddrout) && (iter->size == req->size)) {
> + buf = iter;
> break;
> - buf = NULL;
> + }
> }
> spin_unlock(&fl->lock);
>