Re: [PATCH] staging: vc04_services: shut up out-of-range warning
flat view
From: Dan Carpenter <hidden>
Date: 2021-09-27 12:27:54
Also in:
linux-staging, lkml
On Mon, Sep 27, 2021 at 01:36:56PM +0200, Arnd Bergmann wrote:
quoted hunk ↗ jump to hunk
From: Arnd Bergmann <arnd@arndb.de> The comparison against SIZE_MAX produces a harmless warning on 64-bit architectures: drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c:185:16: error: result of comparison of constant 419244183493398898 with expression of type 'unsigned int' is always false [-Werror,-Wtautological-constant-out-of-range-compare] if (num_pages > (SIZE_MAX - sizeof(struct pagelist) - ~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Shut up that warning by adding a cast to a longer type. Fixes: ca641bae6da9 ("staging: vc04_services: prevent integer overflow in create_pagelist()") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c index b25369a13452..967f10b9582a 100644 --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c@@ -182,7 +182,7 @@ create_pagelist(char *buf, char __user *ubuf, offset = (uintptr_t)ubuf & (PAGE_SIZE - 1); num_pages = DIV_ROUND_UP(count + offset, PAGE_SIZE); - if (num_pages > (SIZE_MAX - sizeof(struct pagelist) - + if ((size_t)num_pages > (SIZE_MAX - sizeof(struct pagelist) - sizeof(struct vchiq_pagelist_info)) / (sizeof(u32) + sizeof(pages[0]) + sizeof(struct scatterlist)))
The temptation would be to declare "num_pages" as size_t instead of adding this cost. But then something will complain about the "pagelistinfo->num_pages = num_pages;" assignment because "pagelistinfo->num_pages" is a u32. The next temptation is to change the SIZE_MAX to UINT_MAX. I didn't do that originally because I can't test this and I was trying not to break things... We probably still don't want to break things, but maybe there is someone who is more familiar with this who knows if UINT_MAX is okay? regards, dan carpenter _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel