From 3d676e458fe0c566f5a62753dc696b6a862fc412 Mon Sep 17 00:00:00 2001 From: Alberto Carboneri Date: Fri, 4 Sep 2026 13:54:37 +0000 Subject: [PATCH] scsi: core: Validate MODE SENSE lengths in scsi_cdl_enable() scsi_cdl_enable() uses length fields returned by MODE SENSE to locate the ATA feature mode page in a 64-byte stack buffer. A target can report a total length shorter than its mode header and block descriptors. The unsigned subtraction used for the MODE SELECT length can wrap, and the separately computed buf_data can point beyond buf. During automatic scan, enable is false, so the read-modify-write of buf_data[4] can clear the low two bits of a target-selected out-of-bounds stack byte. scsi_mode_select() can then copy up to 64 bytes from outside the buffer into the outgoing MODE SELECT payload, disclosing stack contents to the target. This is reachable while scanning a USB storage device that identifies as an ATA device and advertises CDL support. No filesystem mount or userspace access to the block device is required. On upstream commit cee9395acd80 ("Linux 7.3-rc1"), a build-specific, one-vCPU QEMU/Raw Gadget proof using QEMU-only multi-UDC allocator sampling executed a fixed proof command inside the guest and created a UID-0-owned marker during automatic enumeration, with KASLR and NX enabled. The issue was independently found during security research at Drivesec S.r.l. Cap the available length to the buffer size. Validate and consume the mode header and block descriptor lengths before using the page, and require the five bytes needed to access the CDL field. Fixes: 1b22cfb14142 ("scsi: core: Allow enabling and disabling command duration limits") Reported-by: Sashiko AI Review Closes: https://lore.kernel.org/linux-scsi/20260717192313.93D791F000E9@smtp.kernel.org/ Link: https://lore.kernel.org/linux-scsi/20260717222931.AC4EE1F000E9@smtp.kernel.org/ Link: https://lore.kernel.org/linux-scsi/df13ec87ac9b28e3b0a2d9eb26477e276ff0278a.camel@HansenPartnership.com/ Cc: stable@vger.kernel.org Assisted-by: LLM Co-developed-by: Pimen Flavian Dei (Drivesec S.r.l.) Signed-off-by: Pimen Flavian Dei (Drivesec S.r.l.) Signed-off-by: Alberto Carboneri (Drivesec S.r.l.) Link: https://lore.kernel.org/linux-scsi/20260717192313.93D791F000E9@smtp.kernel.org/ Reviewed-by: Damien Le Moal Link: https://patch.msgid.link/20260904135410.360314-1-acarboneri@drivesec.com Signed-off-by: Martin K. Petersen (Oracle) --- drivers/scsi/scsi.c | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-) diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c index 76cdad063f7b..f285521d9de6 100644 --- a/drivers/scsi/scsi.c +++ b/drivers/scsi/scsi.c @@ -727,6 +727,7 @@ int scsi_cdl_enable(struct scsi_device *sdev, bool enable) struct scsi_mode_data data; struct scsi_sense_hdr sshdr; char *buf_data; + size_t avail, offset; int len; ret = scsi_mode_sense(sdev, 0x08, 0x0a, 0xf2, buf, sizeof(buf), @@ -735,11 +736,24 @@ int scsi_cdl_enable(struct scsi_device *sdev, bool enable) return -EINVAL; /* Enable or disable CDL using the ATA feature page */ - len = min_t(size_t, sizeof(buf), - data.length - data.header_length - - data.block_descriptor_length); - buf_data = buf + data.header_length + - data.block_descriptor_length; + avail = min_t(size_t, data.length, sizeof(buf)); + if (data.header_length > avail) + return -EINVAL; + + offset = data.header_length; + avail -= data.header_length; + + if (data.block_descriptor_length > avail) + return -EINVAL; + + offset += data.block_descriptor_length; + avail -= data.block_descriptor_length; + + if (avail < 5) + return -EINVAL; + + buf_data = buf + offset; + len = avail; /* * If we want to enable CDL and CDL is already enabled on the