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Thu, 30 Apr 2026 08:41:03 -0700 (PDT) Received: from localhost.localdomain ([2a00:a041:e04f:2600:a0c9:1d35:8283:f96b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48a820c71c8sm118472015e9.4.2026.04.30.08.41.02 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Thu, 30 Apr 2026 08:41:03 -0700 (PDT) From: "SnailSploit | Kai Aizen" X-Google-Original-From: SnailSploit | Kai Aizen <95986478+SnailSploit@users.noreply.github.com> To: jgg@nvidia.com Cc: kevin.tian@intel.com, nicolinc@nvidia.com, will@kernel.org, robin.murphy@arm.com, joro@8bytes.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, stable@vger.kernel.org, "SnailSploit | Kai Aizen" <95986478+SnailSploit@users.noreply.github.com> Subject: [PATCH] iommufd: Use sizeof(*hdr) instead of sizeof(hdr) in veventq read Date: Thu, 30 Apr 2026 18:41:00 +0300 Message-ID: <20260430154100.61604-1-95986478+SnailSploit@users.noreply.github.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "SnailSploit | Kai Aizen" <95986478+SnailSploit@users.noreply.github.com> The bound-check in iommufd_veventq_fops_read() for the normal vEVENT path uses sizeof(hdr) where the surrounding code uses sizeof(*hdr): if (!vevent_for_lost_events_header(cur) && sizeof(hdr) + cur->data_len > count - done) { hdr is declared as struct iommufd_vevent_header *, so sizeof(hdr) evaluates to the size of the pointer. Surrounding code uses sizeof(*hdr) consistently: if (done >= count || sizeof(*hdr) > count - done) { ... if (copy_to_user(buf + done, hdr, sizeof(*hdr))) { ... done += sizeof(*hdr); struct iommufd_vevent_header is currently 8 bytes (two __u32 fields, flags and sequence), so on 64-bit (sizeof(void *) == 8) the two expressions happen to be equal and the check works as intended. On 32-bit (sizeof(void *) == 4) the check under-counts the header by 4 bytes: a vEVENT whose data_len causes 8 + cur->data_len to exceed count - done while 4 + cur->data_len does not will pass the check, then the loop will copy_to_user 8 bytes of header followed by data_len bytes of payload, writing past the user-supplied buffer. It is also a latent bug for any future expansion of struct iommufd_vevent_header beyond sizeof(void *) on 64-bit; the check should not depend on the type happening to match the host pointer width. Use sizeof(*hdr) to match the rest of the function and the actual amount that will be copied. Fixes: e36ba5ab808e ("iommufd: Add IOMMUFD_OBJ_VEVENTQ and IOMMUFD_CMD_VEVENTQ_ALLOC") Cc: stable@vger.kernel.org Signed-off-by: SnailSploit | Kai Aizen <95986478+SnailSploit@users.noreply.github.com> --- drivers/iommu/iommufd/eventq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/iommu/iommufd/eventq.c b/drivers/iommu/iommufd/eventq.c index 710eef0b6..78689fb52 100644 --- a/drivers/iommu/iommufd/eventq.c +++ b/drivers/iommu/iommufd/eventq.c @@ -321,7 +321,7 @@ static ssize_t iommufd_veventq_fops_read(struct file *filep, char __user *buf, /* If being a normal vEVENT, validate against the full size */ if (!vevent_for_lost_events_header(cur) && - sizeof(hdr) + cur->data_len > count - done) { + sizeof(*hdr) + cur->data_len > count - done) { iommufd_veventq_deliver_restore(veventq, cur); break; } -- 2.43.0