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[112.120.42.27]) by smtp.gmail.com with ESMTPSA id 25sm1603638pjh.57.2020.09.09.02.51.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Sep 2020 02:51:36 -0700 (PDT) From: Peilin Ye To: Jens Axboe Cc: Peilin Ye , Dan Carpenter , Arnd Bergmann , Greg Kroah-Hartman , linux-kernel-mentees@lists.linuxfoundation.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [Linux-kernel-mentees] [PATCH v3] block/scsi-ioctl: Prevent kernel-infoleak in scsi_put_cdrom_generic_arg() Date: Wed, 9 Sep 2020 05:50:57 -0400 Message-Id: <20200909095057.1214104-1-yepeilin.cs@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200727190013.324812-1-yepeilin.cs@gmail.com> References: <20200727190013.324812-1-yepeilin.cs@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org scsi_put_cdrom_generic_arg() is potentially copying uninitialized stack memory to userspace, since the compiler may leave a 3-byte hole in the middle of `cgc32`. Prevent it by adding a padding field to `struct compat_cdrom_generic_command`. Cc: stable@vger.kernel.org Fixes: f3ee6e63a9df ("compat_ioctl: move CDROM_SEND_PACKET handling into scsi") Suggested-by: Dan Carpenter Suggested-by: Arnd Bergmann Signed-off-by: Peilin Ye --- Change in v3: - Improve commit message. scsi_put_cdrom_generic_arg() does not *always* leak kernel information. It is compiler dependent. Reference: https://www.nccgroup.com/us/about-us/newsroom-and-events/blog/2019/october/padding-the-struct-how-a-compiler-optimization-can-disclose-stack-memory/ - Base the patch against mainline 5.9-rc4. Change in v2: - Add a padding field to `struct compat_cdrom_generic_command`, instead of doing memset() on `cgc32`. (Suggested by Jens Axboe ) $ # before $ pahole -C "compat_cdrom_generic_command" !$ pahole -C "compat_cdrom_generic_command" block/scsi_ioctl.o struct compat_cdrom_generic_command { unsigned char cmd[12]; /* 0 12 */ compat_caddr_t buffer; /* 12 4 */ compat_uint_t buflen; /* 16 4 */ compat_int_t stat; /* 20 4 */ compat_caddr_t sense; /* 24 4 */ unsigned char data_direction; /* 28 1 */ /* XXX 3 bytes hole, try to pack */ compat_int_t quiet; /* 32 4 */ compat_int_t timeout; /* 36 4 */ compat_caddr_t reserved[1]; /* 40 4 */ /* size: 44, cachelines: 1, members: 9 */ /* sum members: 41, holes: 1, sum holes: 3 */ /* last cacheline: 44 bytes */ }; $ # after $ pahole -C "compat_cdrom_generic_command" block/scsi_ioctl.o struct compat_cdrom_generic_command { unsigned char cmd[12]; /* 0 12 */ compat_caddr_t buffer; /* 12 4 */ compat_uint_t buflen; /* 16 4 */ compat_int_t stat; /* 20 4 */ compat_caddr_t sense; /* 24 4 */ unsigned char data_direction; /* 28 1 */ unsigned char pad[3]; /* 29 3 */ compat_int_t quiet; /* 32 4 */ compat_int_t timeout; /* 36 4 */ compat_caddr_t reserved[1]; /* 40 4 */ /* size: 44, cachelines: 1, members: 10 */ /* last cacheline: 44 bytes */ }; $ _ block/scsi_ioctl.c | 1 + 1 file changed, 1 insertion(+) diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c index ef722f04f88a..72108404718f 100644 --- a/block/scsi_ioctl.c +++ b/block/scsi_ioctl.c @@ -651,6 +651,7 @@ struct compat_cdrom_generic_command { compat_int_t stat; compat_caddr_t sense; unsigned char data_direction; + unsigned char pad[3]; compat_int_t quiet; compat_int_t timeout; compat_caddr_t reserved[1]; -- 2.25.1