From 1252ede68a386e135123f444e7afa72f93ba14f2 Mon Sep 17 00:00:00 2001 From: Qiu-ji Chen Date: Tue, 11 Mar 2025 08:51:19 +0900 Subject: [PATCH] media: wl128x: Fix atomicity violation in fmc_send_cmd() BugLink: https://bugs.launchpad.net/bugs/2101915 commit ca59f9956d4519ab18ab2270be47c6b8c6ced091 upstream. Atomicity violation occurs when the fmc_send_cmd() function is executed simultaneously with the modification of the fmdev->resp_skb value. Consider a scenario where, after passing the validity check within the function, a non-null fmdev->resp_skb variable is assigned a null value. This results in an invalid fmdev->resp_skb variable passing the validity check. As seen in the later part of the function, skb = fmdev->resp_skb; when the invalid fmdev->resp_skb passes the check, a null pointer dereference error may occur at line 478, evt_hdr = (void *)skb->data; To address this issue, it is recommended to include the validity check of fmdev->resp_skb within the locked section of the function. This modification ensures that the value of fmdev->resp_skb does not change during the validation process, thereby maintaining its validity. This possible bug is found by an experimental static analysis tool developed by our team. This tool analyzes the locking APIs to extract function pairs that can be concurrently executed, and then analyzes the instructions in the paired functions to identify possible concurrency bugs including data races and atomicity violations. Fixes: e8454ff7b9a4 ("[media] drivers:media:radio: wl128x: FM Driver Common sources") Cc: stable@vger.kernel.org Signed-off-by: Qiu-ji Chen Signed-off-by: Hans Verkuil Signed-off-by: Greg Kroah-Hartman CVE-2024-56700 Signed-off-by: Koichiro Den Signed-off-by: Stefan Bader --- drivers/media/radio/wl128x/fmdrv_common.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/media/radio/wl128x/fmdrv_common.c b/drivers/media/radio/wl128x/fmdrv_common.c index 3da8e5102bec..1225dab9fc7d 100644 --- a/drivers/media/radio/wl128x/fmdrv_common.c +++ b/drivers/media/radio/wl128x/fmdrv_common.c @@ -466,11 +466,12 @@ int fmc_send_cmd(struct fmdev *fmdev, u8 fm_op, u16 type, void *payload, jiffies_to_msecs(FM_DRV_TX_TIMEOUT) / 1000); return -ETIMEDOUT; } + spin_lock_irqsave(&fmdev->resp_skb_lock, flags); if (!fmdev->resp_skb) { + spin_unlock_irqrestore(&fmdev->resp_skb_lock, flags); fmerr("Response SKB is missing\n"); return -EFAULT; } - spin_lock_irqsave(&fmdev->resp_skb_lock, flags); skb = fmdev->resp_skb; fmdev->resp_skb = NULL; spin_unlock_irqrestore(&fmdev->resp_skb_lock, flags);