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[76.119.149.155]) by smtp.gmail.com with ESMTPSA id o13sm1330478qko.48.2020.07.29.04.53.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Jul 2020 04:53:17 -0700 (PDT) From: Peilin Ye To: Denis Efremov , 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 v2] block/floppy: Prevent kernel-infoleak in raw_cmd_copyout() Date: Wed, 29 Jul 2020 07:51:57 -0400 Message-Id: <20200729115157.8519-1-yepeilin.cs@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200728141946.426245-1-yepeilin.cs@gmail.com> References: <20200728141946.426245-1-yepeilin.cs@gmail.com> MIME-Version: 1.0 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org raw_cmd_copyout() is potentially copying uninitialized kernel stack memory since it is initializing `cmd` by assignment, which may cause the compiler to leave uninitialized holes in this structure. Fix it by using memcpy() instead. Cc: stable@vger.kernel.org Suggested-by: Dan Carpenter Suggested-by: Arnd Bergmann Signed-off-by: Peilin Ye --- Change in v2: - Remove inappropriate "Fixes:" tag. (Suggested by: Denis Efremov ) Reference: https://lwn.net/Articles/417989/ $ pahole -C "floppy_raw_cmd" drivers/block/floppy.o struct floppy_raw_cmd { unsigned int flags; /* 0 4 */ /* XXX 4 bytes hole, try to pack */ void * data; /* 8 8 */ char * kernel_data; /* 16 8 */ struct floppy_raw_cmd * next; /* 24 8 */ long int length; /* 32 8 */ long int phys_length; /* 40 8 */ int buffer_length; /* 48 4 */ unsigned char rate; /* 52 1 */ unsigned char cmd_count; /* 53 1 */ union { struct { unsigned char cmd[16]; /* 54 16 */ /* --- cacheline 1 boundary (64 bytes) was 6 bytes ago --- */ unsigned char reply_count; /* 70 1 */ unsigned char reply[16]; /* 71 16 */ }; /* 54 33 */ unsigned char fullcmd[33]; /* 54 33 */ }; /* 54 33 */ /* XXX 1 byte hole, try to pack */ /* --- cacheline 1 boundary (64 bytes) was 24 bytes ago --- */ int track; /* 88 4 */ int resultcode; /* 92 4 */ int reserved1; /* 96 4 */ int reserved2; /* 100 4 */ /* size: 104, cachelines: 2, members: 14 */ /* sum members: 99, holes: 2, sum holes: 5 */ /* last cacheline: 40 bytes */ }; drivers/block/floppy.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c index 09079aee8dc4..b8ea98f7a9cb 100644 --- a/drivers/block/floppy.c +++ b/drivers/block/floppy.c @@ -3126,7 +3126,9 @@ static int raw_cmd_copyout(int cmd, void __user *param, int ret; while (ptr) { - struct floppy_raw_cmd cmd = *ptr; + struct floppy_raw_cmd cmd; + + memcpy(&cmd, ptr, sizeof(cmd)); cmd.next = NULL; cmd.kernel_data = NULL; ret = copy_to_user(param, &cmd, sizeof(cmd));