From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 17AA919049B; Thu, 2 Jul 2026 16:43:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783010620; cv=none; b=FBPBkO+r3y+xIkv0Zwr5K/8mJaguDb97jD4jeEvNm3GygPcmtphs/cBhm1PNm3EhPpWhHIK9qCoZ7RQ0qRtduT19fzcSv5v+yw5Muv6dqdY3OP5Ta6zdCci7fwlbFFL9pu1nee7YDtHC7qqBIzElo9zcw0LjEyw+LuIGJwDwIkM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783010620; c=relaxed/simple; bh=JG9HdkEXZ1DUgMHXd4fmR9HOkiAAxTwmxfsb30gcumI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=bgNCVFIJlTjMPzr2cNe2RUt3To42lY2P82tFPYJ5rsxUWDTXD8G2nYsvysgAr9R5DCDlnY4/XykcBaiqcfCAlXM4UH2lQ7stFc+MwT9o6mxIRCB/c+Nf60Lk8E2rOsl3l16lKQSQ0+aeDaojMdPLW5eZPj8mA5mA2tvyghUPb4g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=JuaIDcZ0; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="JuaIDcZ0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7CC9B1F000E9; Thu, 2 Jul 2026 16:43:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1783010619; bh=8O/9tSbKZK+1USmvCixArAZZuQl/Gc4RUC1KZ7N34As=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=JuaIDcZ0IUYwBaZL0TWkIjnbWIwzu27s2sVhifiWR0UdEpQnkMtS2u2V+Onz/ty77 OrXpBVlpavzQ1xpSubfzo/phGju0lYRJNdobmkl7lLl6CABtgB/Q3c6RLb7vQhnMzr f9OsNCzaZGyFatQhVrs5sxW4KXHdod+MIgLz35RU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ashutosh Desai , Sean Christopherson Subject: [PATCH 6.12 178/204] KVM: SVM: Fix page overflow in sev_dbg_crypt() for ENCRYPT path Date: Thu, 2 Jul 2026 18:20:35 +0200 Message-ID: <20260702155122.384519342@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260702155118.667618796@linuxfoundation.org> References: <20260702155118.667618796@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ashutosh Desai commit 78ee2d50185a037b3d2452a97f3dad69c3f7f389 upstream. In sev_dbg_crypt(), the per-iteration transfer length is bounded by the source page offset (PAGE_SIZE - s_off) but not by the destination page offset (PAGE_SIZE - d_off). When d_off > s_off, the encrypt path (__sev_dbg_encrypt_user) performs a read-modify-write using a single-page intermediate buffer (dst_tpage): 1. __sev_dbg_decrypt() expands the size to round_up(len + (d_off & 15), 16) before issuing the PSP command. If len + (d_off & 15) > PAGE_SIZE, the PSP writes beyond the end of the 4096-byte dst_tpage allocation. 2. The subsequent memcpy()/copy_from_user() into page_address(dst_tpage) + (d_off & 15) of 'len' bytes overflows by up to 15 bytes under the same condition. Trigger example: s_off = 0, d_off = 1, debug.len = PAGE_SIZE - the PSP is instructed to write round_up(4097, 16) = 4112 bytes to a 4096-byte buffer. Fix by also bounding len by (PAGE_SIZE - d_off), the same check that sev_send_update_data() already performs for its single-page guest region. ================================================================== BUG: KASAN: slab-use-after-free in sev_dbg_crypt+0x993/0xd10 [kvm_amd] Write of size 4095 at addr ff110062293bb009 by task sev_dbg_test/228214 CPU: 96 UID: 0 PID: 228214 Comm: sev_dbg_test Tainted: G U W 7.0.0-smp--5ce9b0c48211-dbg #156 PREEMPTLAZY Tainted: [U]=USER, [W]=WARN Hardware name: Google Astoria/astoria, BIOS 0.20250817.1-0 08/25/2025 Call Trace: dump_stack_lvl+0x54/0x70 print_report+0xbc/0x260 kasan_report+0xa2/0xd0 kasan_check_range+0x25f/0x2c0 __asan_memcpy+0x40/0x70 sev_dbg_crypt+0x993/0xd10 [kvm_amd] sev_mem_enc_ioctl+0x33c/0x450 [kvm_amd] kvm_vm_ioctl+0x65d/0x6d0 [kvm] __se_sys_ioctl+0xb2/0x100 do_syscall_64+0xe8/0x870 entry_SYSCALL_64_after_hwframe+0x4b/0x53 The buggy address belongs to the physical page: page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x7fe72b6a0 pfn:0x62293bb memcg:ff11000112827d82 flags: 0x1400000000000000(node=1|zone=1) raw: 1400000000000000 0000000000000000 dead000000000122 0000000000000000 raw: 00000007fe72b6a0 0000000000000000 00000001ffffffff ff11000112827d82 page dumped because: kasan: bad access detected Memory state around the buggy address: ff110062293bbf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ff110062293bbf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ff110062293bc000: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ^ ff110062293bc080: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ff110062293bc100: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ================================================================== Disabling lock debugging due to kernel taint Fixes: 24f41fb23a39 ("KVM: SVM: Add support for SEV DEBUG_DECRYPT command") Fixes: 7d1594f5d94b ("KVM: SVM: Add support for SEV DEBUG_ENCRYPT command") Cc: stable@vger.kernel.org Signed-off-by: Ashutosh Desai [sean: add sample KASAN splat, Fixes, and stable@] Link: https://patch.msgid.link/20260501203537.2120074-2-seanjc@google.com Signed-off-by: Sean Christopherson Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/svm/sev.c | 1 + 1 file changed, 1 insertion(+) --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -1280,6 +1280,7 @@ static int sev_dbg_crypt(struct kvm *kvm s_off = vaddr & ~PAGE_MASK; d_off = dst_vaddr & ~PAGE_MASK; len = min_t(size_t, (PAGE_SIZE - s_off), size); + len = min_t(size_t, len, PAGE_SIZE - d_off); if (dec) ret = __sev_dbg_decrypt_user(kvm,