From: Xiaomeng Tong xiam0nd.tong@gmail.com
[ Upstream commit 261f33388c29f6f3c12a724e6d89172b7f6d5996 ]
The list iterator will point to a bogus position containing HEAD if the list is empty or the element is not found in list. This case should be checked before any use of the iterator, otherwise it will lead to a invalid memory access. The missing check here is before "pin = iterm->id;", just add check here to fix the security bug.
In addition, the list iterator value 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 element is not found in list, considering the (mis)use here: "if (iterm == NULL".
Use a new value 'it' as the list iterator, while use the old value 'iterm' as a dedicated pointer to point to the found element, which 1. can fix this bug, due to 'iterm' is NULL only if it's not found. 2. do not need to change all the uses of 'iterm' after the loop. 3. can also limit the scope of the list iterator 'it' *only inside* the traversal loop by simply declaring 'it' inside the loop in the future, as usage of the iterator outside of the list_for_each_entry is considered harmful. https://lkml.org/lkml/2022/2/17/1032
Fixes: d5e90b7a6cd1c ("[media] uvcvideo: Move to video_ioctl2") Signed-off-by: Xiaomeng Tong xiam0nd.tong@gmail.com Signed-off-by: Laurent Pinchart laurent.pinchart@ideasonboard.com Signed-off-by: Mauro Carvalho Chehab mchehab@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/media/usb/uvc/uvc_v4l2.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c index 2b0ca32d7196..800b37a5bbe8 100644 --- a/drivers/media/usb/uvc/uvc_v4l2.c +++ b/drivers/media/usb/uvc/uvc_v4l2.c @@ -841,29 +841,31 @@ static int uvc_ioctl_enum_input(struct file *file, void *fh, struct uvc_video_chain *chain = handle->chain; const struct uvc_entity *selector = chain->selector; struct uvc_entity *iterm = NULL; + struct uvc_entity *it; u32 index = input->index; - int pin = 0;
if (selector == NULL || (chain->dev->quirks & UVC_QUIRK_IGNORE_SELECTOR_UNIT)) { if (index != 0) return -EINVAL; - list_for_each_entry(iterm, &chain->entities, chain) { - if (UVC_ENTITY_IS_ITERM(iterm)) + list_for_each_entry(it, &chain->entities, chain) { + if (UVC_ENTITY_IS_ITERM(it)) { + iterm = it; break; + } } - pin = iterm->id; } else if (index < selector->bNrInPins) { - pin = selector->baSourceID[index]; - list_for_each_entry(iterm, &chain->entities, chain) { - if (!UVC_ENTITY_IS_ITERM(iterm)) + list_for_each_entry(it, &chain->entities, chain) { + if (!UVC_ENTITY_IS_ITERM(it)) continue; - if (iterm->id == pin) + if (it->id == selector->baSourceID[index]) { + iterm = it; break; + } } }
- if (iterm == NULL || iterm->id != pin) + if (iterm == NULL) return -EINVAL;
memset(input, 0, sizeof(*input));