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([2a01:cb1c:263:8800:8714:9136:d3b4:25b3]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-493e0aa7da9sm39974375e9.1.2026.07.07.01.31.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 07 Jul 2026 01:31:01 -0700 (PDT) Message-ID: <64455e5d-4b1e-4cf7-8aec-0b1aacf89cce@redhat.com> Date: Tue, 7 Jul 2026 10:30:59 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/5] hw/arm/smmuv3: Sanitize SMMU_S_STRTAB_BASE_CFG.LOG2SIZE Content-Language: en-US To: Peter Maydell Cc: eric.auger.pro@gmail.com, qemu-devel@nongnu.org, qemu-arm@nongnu.org, berrange@redhat.com, skolothumtho@nvidia.com, nicolinc@nvidia.com, nathanc@nvidia.com References: <20260701091209.2860306-1-eric.auger@redhat.com> <20260701091209.2860306-4-eric.auger@redhat.com> From: Eric Auger In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=eric.auger@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.445, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: eric.auger@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Hi Shameer, Peter, On 7/3/26 2:54 PM, Peter Maydell wrote: > On Wed, 1 Jul 2026 at 10:12, Eric Auger wrote: >> STRTAB_BASE_CFG.LOG2SIZE is programmed by the guest through the >> emulated SMMUv3 MMIO register interface. Currently the value is >> not checked and used directly in smmu_find_ste() for strtab_base >> alignment computation with risk that MAKE_64BIT_MASK() runs out >> of bounds. On FMT==1 the strtab_size cannot be greater than 64 after >> the SPLIT being at minimum 6 (log2size is max 64). >> >> However on FMT=0 path, strtab_size= log2size + 6 can potentially >> exceed 64. Let's abort in that case. >> >> Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3632 >> Signed-off-by: Eric Auger >> --- >> hw/arm/smmuv3.c | 8 ++++++++ >> 1 file changed, 8 insertions(+) >> >> diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c >> index 285e6164a07..5ec3700d0d5 100644 >> --- a/hw/arm/smmuv3.c >> +++ b/hw/arm/smmuv3.c >> @@ -1696,6 +1696,14 @@ static MemTxResult smmu_writel(SMMUv3State *s, hwaddr offset, >> s->sid_split = 6; >> } >> s->features |= SMMU_FEATURE_2LVL_STE; >> + } else { >> + uint32_t log2size = FIELD_EX32(data, STRTAB_BASE_CFG, LOG2SIZE); >> + >> + if (log2size + 6 > 64) { >> + qemu_log_mask(LOG_GUEST_ERROR, >> + "Invalid STRTAB_BASE_CFG.LOG2SIZE: %d", log2size); >> + g_assert_not_reached(); > This doesn't look right. Either: > (a) the guest can do something silly that gets us to this code path: > in that case we mustn't assert, but must continue (doing whatever > the spec permits and that is reasonably straightforward to implement) Sorry for the delay OK. Then I will just follow Shameer's suggestion and cap strtab_size to 64. Thanks! Eric > (b) we can't actually get here in practice: in that case the logging > isn't needed and we could just assert(log2size + 6 <= 64); > > It sounds like we're in case (a) here. > > thanks > -- PMM >