linux-kernel - [PATCH] scsi: ses: Fix out-of-bounds memory access in ses_enclosure_data

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Date:   Wed,  1 May 2019 14:05:35 -0400
From:   Waiman Long <longman@...hat.com>
To:     "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Waiman Long <longman@...hat.com>
Subject: [PATCH] scsi: ses: Fix out-of-bounds memory access in ses_enclosure_data_process()

KASAN has found a slab-out-of-bounds error in ses_enclosure_data_process().

[   27.298092] BUG: KASAN: slab-out-of-bounds in ses_enclosure_data_process+0x919/0xe80 [ses]
[   27.306407] Read of size 1 at addr ffff8807c99048b1 by task systemd-udevd/1563
[   27.315173] CPU: 18 PID: 1563 Comm: systemd-udevd Not tainted 4.18.0-80.23.el8.x86_64+debug #1
[   27.323835] Hardware name: HPE ProLiant XL450 Gen10/ProLiant XL450 Gen10, BIOS U40 10/02/2018
[   27.332410] Call Trace:
  :
[   27.348557]  kasan_report.cold.6+0x92/0x1a6
[   27.352771]  ses_enclosure_data_process+0x919/0xe80 [ses]
[   27.358211]  ? kfree+0xd6/0x2e0
[   27.361376]  ses_intf_add+0xa23/0xef1 [ses]
[   27.365590]  ? class_dev_iter_next+0x6c/0xc0
[   27.370034]  class_interface_register+0x298/0x400
[   27.374769]  ? tsc_cs_mark_unstable+0x60/0x60
[   27.379163]  ? class_dev_iter_exit+0x10/0x10
[   27.384857]  ? 0xffffffffc0838000
[   27.389580]  ses_init+0x12/0x1000 [ses]
[   27.394832]  do_one_initcall+0xe9/0x5fd
  :
[   27.562322] Allocated by task 1563:
[   27.562330]  kasan_kmalloc+0xbf/0xe0
[   27.569433]  __kmalloc+0x150/0x360
[   27.572858]  ses_intf_add+0x76a/0xef1 [ses]
[   27.577068]  class_interface_register+0x298/0x400
[   27.581803]  ses_init+0x12/0x1000 [ses]
[   27.587053]  do_one_initcall+0xe9/0x5fd
[   27.592309]  do_init_module+0x1f2/0x710
[   27.597564]  load_module+0x3e19/0x5910
[   27.601336]  __do_sys_init_module+0x1dd/0x260
[   27.606673]  do_syscall_64+0xa5/0x4a0
[   27.610359]  entry_SYSCALL_64_after_hwframe+0x6a/0xdf
  :
[   27.624932] The buggy address belongs to the object at ffff8807c9904400
                which belongs to the cache kmalloc-2048 of size 2048
[   27.637701] The buggy address is located 1201 bytes inside of
                2048-byte region [ffff8807c9904400, ffff8807c9904c00)
[   27.649683] The buggy address belongs to the page:
[   27.654503] page:ffffea001f264000 count:1 mapcount:0 mapping:ffff880107c15d80 index:0x0 compound_mapcount: 0
[   27.664393] flags: 0x17ffffc0008100(slab|head)
[   27.668865] raw: 0017ffffc0008100 dead000000000100 dead000000000200 ffff880107c15d80
[   27.676656] raw: 0000000000000000 00000000800f000f 00000001ffffffff 0000000000000000
[   27.684444] page dumped because: kasan: bad access detected

The out-of-bounds memory access happens to ses_dev->page10 which has a
size of 1200 bytes in this case. The invalid memory access happens in:

 600 if (addl_desc_ptr &&
 601     /* only find additional descriptions for specific devices */
 602     (type_ptr[0] == ENCLOSURE_COMPONENT_DEVICE ||
 603      type_ptr[0] == ENCLOSURE_COMPONENT_ARRAY_DEVICE ||
 604      type_ptr[0] == ENCLOSURE_COMPONENT_SAS_EXPANDER ||
 605      /* these elements are optional */
 606      type_ptr[0] == ENCLOSURE_COMPONENT_SCSI_TARGET_PORT ||
 607      type_ptr[0] == ENCLOSURE_COMPONENT_SCSI_INITIATOR_PORT ||
 608      type_ptr[0] == ENCLOSURE_COMPONENT_CONTROLLER_ELECTRONICS))
 609         addl_desc_ptr += addl_desc_ptr[1] + 2; <-- here

To fix the out-of-bounds memory access, code is now added to make sure
that addl_desc_ptr will never point to an address outside of its bounds.

With this patch, the KASAN warning is gone.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 drivers/scsi/ses.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/ses.c b/drivers/scsi/ses.c
index 0fc39224ce1e..dbc9acc2df2f 100644
--- a/drivers/scsi/ses.c
+++ b/drivers/scsi/ses.c
@@ -605,9 +605,14 @@ static void ses_enclosure_data_process(struct enclosure_device *edev,
 			     /* these elements are optional */
 			     type_ptr[0] == ENCLOSURE_COMPONENT_SCSI_TARGET_PORT ||
 			     type_ptr[0] == ENCLOSURE_COMPONENT_SCSI_INITIATOR_PORT ||
-			     type_ptr[0] == ENCLOSURE_COMPONENT_CONTROLLER_ELECTRONICS))
+			     type_ptr[0] == ENCLOSURE_COMPONENT_CONTROLLER_ELECTRONICS)) {
 				addl_desc_ptr += addl_desc_ptr[1] + 2;
 
+				/* Ensure no out-of-bounds memory access */
+				if (addl_desc_ptr >= ses_dev->page10 +
+						     ses_dev->page10_len)
+					addl_desc_ptr = NULL;
+			}
 		}
 	}
 	kfree(buf);
-- 
2.18.1