[PATCH 6.18 335/752] misc: bcm_vk: Fix possible null-pointer dereferences in bcm_vk_read()

Sasha Levin
2026-02-28T17:52:49Z

From: Tuo Li <islituo@gmail.com>

[ Upstream commit ba75ecb97d3f4e95d59002c13afb6519205be6cb ]

In the function bcm_vk_read(), the pointer entry is checked, indicating
that it can be NULL. If entry is NULL and rc is set to -EMSGSIZE, the
following code may cause null-pointer dereferences:

struct vk_msg_blk tmp_msg = entry->to_h_msg[0];
set_msg_id(&tmp_msg, entry->usr_msg_id);
tmp_msg.size = entry->to_h_blks - 1;

To prevent these possible null-pointer dereferences, copy to_h_msg,
usr_msg_id, and to_h_blks from iter into temporary variables, and return
these temporary variables to the application instead of accessing them
through a potentially NULL entry.

Signed-off-by: Tuo Li <islituo@gmail.com>
Reviewed-by: Scott Branden <scott.branden@broadcom.com>
Link: https://patch.msgid.link/20251211063637.3987937-1-islituo@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/misc/bcm-vk/bcm_vk_msg.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/bcm-vk/bcm_vk_msg.c b/drivers/misc/bcm-vk/bcm_vk_msg.c
index 1f42d1d5a630a..665a3888708ac 100644
--- a/drivers/misc/bcm-vk/bcm_vk_msg.c
+++ b/drivers/misc/bcm-vk/bcm_vk_msg.c
@@ -1010,6 +1010,9 @@ ssize_t bcm_vk_read(struct file *p_file,
struct device *dev = &vk->pdev->dev;
struct bcm_vk_msg_chan *chan = &vk->to_h_msg_chan;
struct bcm_vk_wkent *entry = NULL, *iter;
+ struct vk_msg_blk tmp_msg;
+ u32 tmp_usr_msg_id;
+ u32 tmp_blks;
u32 q_num;
u32 rsp_length;

@@ -1034,6 +1037,9 @@ ssize_t bcm_vk_read(struct file *p_file,
entry = iter;
} else {
/* buffer not big enough */
+ tmp_msg = iter->to_h_msg[0];
+ tmp_usr_msg_id = iter->usr_msg_id;
+ tmp_blks = iter->to_h_blks;
rc = -EMSGSIZE;
}
goto read_loop_exit;
@@ -1052,14 +1058,12 @@ ssize_t bcm_vk_read(struct file *p_file,

bcm_vk_free_wkent(dev, entry);
} else if (rc == -EMSGSIZE) {
- struct vk_msg_blk tmp_msg = entry->to_h_msg[0];
-
/*
* in this case, return just the first block, so
* that app knows what size it is looking for.
*/
- set_msg_id(&tmp_msg, entry->usr_msg_id);
- tmp_msg.size = entry->to_h_blks - 1;
+ set_msg_id(&tmp_msg, tmp_usr_msg_id);
+ tmp_msg.size = tmp_blks - 1;
if (copy_to_user(buf, &tmp_msg, VK_MSGQ_BLK_SIZE) != 0) {
dev_err(dev, "Error return 1st block in -EMSGSIZE\n");
rc = -EFAULT;
--
2.51.0