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Wed, 22 Jul 2026 08:58:34 -0700 (PDT) Date: Wed, 22 Jul 2026 08:58:33 -0700 In-Reply-To: <6a426dd2.854d4ab9.360e1d.0008.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a60e8a9.33ea6125.251e5.000b.GAE@google.com> Subject: Forwarded: Re: [syzbot] [kvm-x86?] KASAN: use-after-free Read in kvm_setup_guest_pvclock From: syzbot To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com. *** Subject: Re: [syzbot] [kvm-x86?] KASAN: use-after-free Read in kvm_setup_guest_pvclock Author: halves@igalia.com #syz test Reported-by: syzbot+fb7c2dd166d3ea63df2a@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?extid=fb7c2dd166d3ea63df2a Signed-off-by: Heitor Alves de Siqueira --- drivers/gpu/drm/drm_mode_config.c | 4 ++-- virt/kvm/pfncache.c | 28 ++++++++++++++++++++++++++++ 2 files changed, 30 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c index 3bcc7bf0900c..e06f1cd149a7 100644 --- a/drivers/gpu/drm/drm_mode_config.c +++ b/drivers/gpu/drm/drm_mode_config.c @@ -869,8 +869,8 @@ static void validate_blend_mode_for_alpha_formats(struct drm_plane *plane) for (i = 0; i < plane->format_count; i++) { fmt = drm_format_info(plane->format_types[i]); if (fmt->has_alpha) { - WARN(1, "[PLANE:%d:%s] pixel format with alpha exposed but blend mode not setup", - plane->base.id, plane->name); + /* WARN(1, "[PLANE:%d:%s] pixel format with alpha exposed but blend mode not setup", */ + /* plane->base.id, plane->name); */ break; } } diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c index 728d2c1b488a..8a766c4cd4bd 100644 --- a/virt/kvm/pfncache.c +++ b/virt/kvm/pfncache.c @@ -152,6 +152,32 @@ static inline bool mmu_notifier_retry_cache(struct kvm *kvm, unsigned long mmu_s return kvm->mmu_invalidate_seq != mmu_seq; } +static void kvm_gpc_invalidate_pfn(struct kvm *kvm, kvm_pfn_t pfn) +{ + struct gfn_to_pfn_cache *gpc; + + if (is_error_noslot_pfn(pfn)) + return; + + spin_lock(&kvm->gpc_lock); + list_for_each_entry(gpc, &kvm->gpc_list, list) { + read_lock_irq(&gpc->lock); + + if (gpc->valid && gpc->pfn == pfn) { + read_unlock_irq(&gpc->lock); + + write_lock_irq(&gpc->lock); + if (gpc->valid && gpc->pfn == pfn) + gpc->valid = false; + write_unlock_irq(&gpc->lock); + continue; + } + + read_unlock_irq(&gpc->lock); + } + spin_unlock(&kvm->gpc_lock); +} + static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc) { /* Note, the new page offset may be different than the old! */ @@ -201,6 +227,7 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc) if (new_khva != old_khva) gpc_unmap(new_pfn, new_khva); + kvm_gpc_invalidate_pfn(gpc->kvm, new_pfn); kvm_release_page_unused(page); cond_resched(); @@ -221,6 +248,7 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc) new_khva = gpc_map(new_pfn); if (!new_khva) { + kvm_gpc_invalidate_pfn(gpc->kvm, new_pfn); kvm_release_page_unused(page); goto out_error; } -- 2.55.0