Revision 2172fa709ab32ca60e86179dc67d0857be8e2c98 authored by Stephen Smalley on 30 January 2014, 16:26:59 UTC, committed by Paul Moore on 05 February 2014, 17:20:51 UTC
Setting an empty security context (length=0) on a file will lead to incorrectly dereferencing the type and other fields of the security context structure, yielding a kernel BUG. As a zero-length security context is never valid, just reject all such security contexts whether coming from userspace via setxattr or coming from the filesystem upon a getxattr request by SELinux. Setting a security context value (empty or otherwise) unknown to SELinux in the first place is only possible for a root process (CAP_MAC_ADMIN), and, if running SELinux in enforcing mode, only if the corresponding SELinux mac_admin permission is also granted to the domain by policy. In Fedora policies, this is only allowed for specific domains such as livecd for setting down security contexts that are not defined in the build host policy. Reproducer: su setenforce 0 touch foo setfattr -n security.selinux foo Caveat: Relabeling or removing foo after doing the above may not be possible without booting with SELinux disabled. Any subsequent access to foo after doing the above will also trigger the BUG. BUG output from Matthew Thode: [ 473.893141] ------------[ cut here ]------------ [ 473.962110] kernel BUG at security/selinux/ss/services.c:654! [ 473.995314] invalid opcode: 0000 [#6] SMP [ 474.027196] Modules linked in: [ 474.058118] CPU: 0 PID: 8138 Comm: ls Tainted: G D I 3.13.0-grsec #1 [ 474.116637] Hardware name: Supermicro X8ST3/X8ST3, BIOS 2.0 07/29/10 [ 474.149768] task: ffff8805f50cd010 ti: ffff8805f50cd488 task.ti: ffff8805f50cd488 [ 474.183707] RIP: 0010:[<ffffffff814681c7>] [<ffffffff814681c7>] context_struct_compute_av+0xce/0x308 [ 474.219954] RSP: 0018:ffff8805c0ac3c38 EFLAGS: 00010246 [ 474.252253] RAX: 0000000000000000 RBX: ffff8805c0ac3d94 RCX: 0000000000000100 [ 474.287018] RDX: ffff8805e8aac000 RSI: 00000000ffffffff RDI: ffff8805e8aaa000 [ 474.321199] RBP: ffff8805c0ac3cb8 R08: 0000000000000010 R09: 0000000000000006 [ 474.357446] R10: 0000000000000000 R11: ffff8805c567a000 R12: 0000000000000006 [ 474.419191] R13: ffff8805c2b74e88 R14: 00000000000001da R15: 0000000000000000 [ 474.453816] FS: 00007f2e75220800(0000) GS:ffff88061fc00000(0000) knlGS:0000000000000000 [ 474.489254] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 474.522215] CR2: 00007f2e74716090 CR3: 00000005c085e000 CR4: 00000000000207f0 [ 474.556058] Stack: [ 474.584325] ffff8805c0ac3c98 ffffffff811b549b ffff8805c0ac3c98 ffff8805f1190a40 [ 474.618913] ffff8805a6202f08 ffff8805c2b74e88 00068800d0464990 ffff8805e8aac860 [ 474.653955] ffff8805c0ac3cb8 000700068113833a ffff880606c75060 ffff8805c0ac3d94 [ 474.690461] Call Trace: [ 474.723779] [<ffffffff811b549b>] ? lookup_fast+0x1cd/0x22a [ 474.778049] [<ffffffff81468824>] security_compute_av+0xf4/0x20b [ 474.811398] [<ffffffff8196f419>] avc_compute_av+0x2a/0x179 [ 474.843813] [<ffffffff8145727b>] avc_has_perm+0x45/0xf4 [ 474.875694] [<ffffffff81457d0e>] inode_has_perm+0x2a/0x31 [ 474.907370] [<ffffffff81457e76>] selinux_inode_getattr+0x3c/0x3e [ 474.938726] [<ffffffff81455cf6>] security_inode_getattr+0x1b/0x22 [ 474.970036] [<ffffffff811b057d>] vfs_getattr+0x19/0x2d [ 475.000618] [<ffffffff811b05e5>] vfs_fstatat+0x54/0x91 [ 475.030402] [<ffffffff811b063b>] vfs_lstat+0x19/0x1b [ 475.061097] [<ffffffff811b077e>] SyS_newlstat+0x15/0x30 [ 475.094595] [<ffffffff8113c5c1>] ? __audit_syscall_entry+0xa1/0xc3 [ 475.148405] [<ffffffff8197791e>] system_call_fastpath+0x16/0x1b [ 475.179201] Code: 00 48 85 c0 48 89 45 b8 75 02 0f 0b 48 8b 45 a0 48 8b 3d 45 d0 b6 00 8b 40 08 89 c6 ff ce e8 d1 b0 06 00 48 85 c0 49 89 c7 75 02 <0f> 0b 48 8b 45 b8 4c 8b 28 eb 1e 49 8d 7d 08 be 80 01 00 00 e8 [ 475.255884] RIP [<ffffffff814681c7>] context_struct_compute_av+0xce/0x308 [ 475.296120] RSP <ffff8805c0ac3c38> [ 475.328734] ---[ end trace f076482e9d754adc ]--- Reported-by: Matthew Thode <mthode@mthode.org> Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> Cc: stable@vger.kernel.org Signed-off-by: Paul Moore <pmoore@redhat.com>
1 parent 6a96e15
sun_uflash.c
/* sun_uflash.c - Driver for user-programmable flash on
* Sun Microsystems SME boardsets.
*
* This driver does NOT provide access to the OBP-flash for
* safety reasons-- use <linux>/drivers/sbus/char/flash.c instead.
*
* Copyright (c) 2001 Eric Brower (ebrower@usa.net)
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/ioport.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/slab.h>
#include <asm/prom.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/map.h>
#define UFLASH_OBPNAME "flashprom"
#define DRIVER_NAME "sun_uflash"
#define PFX DRIVER_NAME ": "
#define UFLASH_WINDOW_SIZE 0x200000
#define UFLASH_BUSWIDTH 1 /* EBus is 8-bit */
MODULE_AUTHOR("Eric Brower <ebrower@usa.net>");
MODULE_DESCRIPTION("User-programmable flash device on Sun Microsystems boardsets");
MODULE_SUPPORTED_DEVICE(DRIVER_NAME);
MODULE_LICENSE("GPL");
MODULE_VERSION("2.1");
struct uflash_dev {
const char *name; /* device name */
struct map_info map; /* mtd map info */
struct mtd_info *mtd; /* mtd info */
};
struct map_info uflash_map_templ = {
.name = "SUNW,???-????",
.size = UFLASH_WINDOW_SIZE,
.bankwidth = UFLASH_BUSWIDTH,
};
int uflash_devinit(struct platform_device *op, struct device_node *dp)
{
struct uflash_dev *up;
if (op->resource[1].flags) {
/* Non-CFI userflash device-- once I find one we
* can work on supporting it.
*/
printk(KERN_ERR PFX "Unsupported device at %s, 0x%llx\n",
dp->full_name, (unsigned long long)op->resource[0].start);
return -ENODEV;
}
up = kzalloc(sizeof(struct uflash_dev), GFP_KERNEL);
if (!up) {
printk(KERN_ERR PFX "Cannot allocate struct uflash_dev\n");
return -ENOMEM;
}
/* copy defaults and tweak parameters */
memcpy(&up->map, &uflash_map_templ, sizeof(uflash_map_templ));
up->map.size = resource_size(&op->resource[0]);
up->name = of_get_property(dp, "model", NULL);
if (up->name && 0 < strlen(up->name))
up->map.name = (char *)up->name;
up->map.phys = op->resource[0].start;
up->map.virt = of_ioremap(&op->resource[0], 0, up->map.size,
DRIVER_NAME);
if (!up->map.virt) {
printk(KERN_ERR PFX "Failed to map device.\n");
kfree(up);
return -EINVAL;
}
simple_map_init(&up->map);
/* MTD registration */
up->mtd = do_map_probe("cfi_probe", &up->map);
if (!up->mtd) {
of_iounmap(&op->resource[0], up->map.virt, up->map.size);
kfree(up);
return -ENXIO;
}
up->mtd->owner = THIS_MODULE;
mtd_device_register(up->mtd, NULL, 0);
dev_set_drvdata(&op->dev, up);
return 0;
}
static int uflash_probe(struct platform_device *op)
{
struct device_node *dp = op->dev.of_node;
/* Flashprom must have the "user" property in order to
* be used by this driver.
*/
if (!of_find_property(dp, "user", NULL))
return -ENODEV;
return uflash_devinit(op, dp);
}
static int uflash_remove(struct platform_device *op)
{
struct uflash_dev *up = dev_get_drvdata(&op->dev);
if (up->mtd) {
mtd_device_unregister(up->mtd);
map_destroy(up->mtd);
}
if (up->map.virt) {
of_iounmap(&op->resource[0], up->map.virt, up->map.size);
up->map.virt = NULL;
}
kfree(up);
return 0;
}
static const struct of_device_id uflash_match[] = {
{
.name = UFLASH_OBPNAME,
},
{},
};
MODULE_DEVICE_TABLE(of, uflash_match);
static struct platform_driver uflash_driver = {
.driver = {
.name = DRIVER_NAME,
.owner = THIS_MODULE,
.of_match_table = uflash_match,
},
.probe = uflash_probe,
.remove = uflash_remove,
};
module_platform_driver(uflash_driver);
Computing file changes ...
