From: Peilin Ye <yepeilin.cs@gmail.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: Arnd Bergmann <arnd@arndb.de>,
linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
linux-kernel-mentees@lists.linuxfoundation.org,
Peilin Ye <yepeilin.cs@gmail.com>,
Dan Carpenter <dan.carpenter@oracle.com>
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 [thread overview]
Message-ID: <20200909095057.1214104-1-yepeilin.cs@gmail.com> (raw)
In-Reply-To: <20200727190013.324812-1-yepeilin.cs@gmail.com>
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 <dan.carpenter@oracle.com>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
---
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
<axboe@kernel.dk>)
$ # 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
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prev parent reply other threads:[~2020-09-09 9:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-27 16:19 [Linux-kernel-mentees] [PATCH] block/scsi-ioctl: Prevent kernel-infoleak in scsi_put_cdrom_generic_arg() Peilin Ye
2020-07-27 16:25 ` Jens Axboe
2020-07-27 19:00 ` [Linux-kernel-mentees] [PATCH v2] " Peilin Ye
2020-09-09 9:50 ` Peilin Ye [this message]
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