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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 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. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel