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Mon, 19 Oct 2026 07:55:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1792421706; bh=JePCMnx8/su8AAS/ZVIThUJhxAH7QCVSw2VlUvAcrQc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=dquZ0zsb8TUxQqrVKFHzKecjJPxmFn9BPWmSPeUt4pp2uBPq8APeVyzMisLgssh1v TZU/WEC3H5pP58oL4cP/OjMccLrvXkUY+5HU52USqCNbPlN+hEGwvXf1yR7AkaGpR7 gskM7Oy6PccGDnhdnyilm74wYQa3HEvySaszSEwE= Message-ID: <45c5ebc9-a4d2-44e6-a08f-79676ecb0579@arm.com> Date: Mon, 19 Oct 2026 20:24:57 +0530 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/5] mm/kmsan: undo the shadow mapping when the origin mapping fails To: Hao Ge , Suren Baghdasaryan , Uladzislau Rezki , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , "Ritesh Harjani (IBM)" , Shrikanth Hegde , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Andrew Morton , Dennis Zhou , Tejun Heo , Christoph Lameter Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, stable@vger.kernel.org References: <20261019054531.87652-1-hao.ge@linux.dev> <20261019054531.87652-2-hao.ge@linux.dev> Content-Language: en-US From: Dev Jain In-Reply-To: <20261019054531.87652-2-hao.ge@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 19/10/26 11:15 am, Hao Ge wrote: > kmsan_vmap_pages_range_noflush() first maps the shadow pages and then > the origin pages. If the second mapping fails, the first one is left > mapped, and the callers do not roll it back. The next vmap of the > same metadata range hits the stale PTEs again and BUG()s on the huge > mapping path, or gets -EBUSY with a WARN_ON() on the small page one. > > Undo the shadow mapping on that error path, the same way > kmsan_ioremap_page_range() cleans up after a partial failure. > __vunmap_range_noflush() only clears the PTEs; nothing has touched > the shadow mapping, so no TLB flush is needed. > > Fixes: 47ebd0310e89 ("mm: kmsan: handle alloc failures in kmsan_vmap_pages_range_noflush()") > Cc: stable@vger.kernel.org > Reviewed-by: Suren Baghdasaryan > Signed-off-by: Hao Ge > --- Reviewed-by: Dev Jain > mm/kmsan/shadow.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/mm/kmsan/shadow.c b/mm/kmsan/shadow.c > index 0c88d89bf0d6..2166086d3dc3 100644 > --- a/mm/kmsan/shadow.c > +++ b/mm/kmsan/shadow.c > @@ -258,6 +258,10 @@ int kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end, > o_pages, page_shift); > kmsan_leave_runtime(); > if (mapped) { > + /* Undo the shadow mapping set up above. */ > + kmsan_enter_runtime(); > + __vunmap_range_noflush(shadow_start, shadow_end); > + kmsan_leave_runtime(); > err = mapped; > goto ret; > }