On Tue, Apr 14, 2020 at 04:10:35PM +0100, Will Deacon wrote:
On Tue, Apr 14, 2020 at 03:53:45PM +0100, Vincenzo Frascino wrote:
On 4/14/20 2:27 PM, Mark Rutland wrote:
On Tue, Apr 14, 2020 at 01:50:38PM +0100, Vincenzo Frascino wrote:
On 4/14/20 11:42 AM, Mark Rutland wrote:
The aarch32_vdso_pages[] array never has entries allocated in the C_VVAR or C_VDSO slots, and as the array is zero initialized these contain NULL.
However in __aarch32_alloc_vdso_pages() when aarch32_alloc_kuser_vdso_page() fails we attempt to free the page whose struct page is at NULL, which is obviously nonsensical.
Could you please explain why do you think that free(NULL) is "nonsensical"?
Regardless of the below, can you please explain why it is sensical? I'm struggling to follow your argument here.
free(NULL) is a no-operation ("no action occurs") according to the C standard (ISO-IEC 9899 paragraph 7.20.3.2). Hence this should not cause any bug if the allocator is correctly implemented. From what I can see the implementation of the page allocator honors this assumption.
Since you say it is a bug (providing evidence), we might have to investigate because probably there is an issue somewhere else.
Not sure why you feel the need to throw the C standard around -- the patch from Mark looks obviously like the right thing to do to me, so:
Acked-by: Will Deacon will@kernel.org
Catalin -- please take this one as a fix so that I can queue the rest of the patches for 5.8 once it's hit mainline.
I queued this patch for -rc2. Thanks.