From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Jann Horn <jannh@google.com>,
Douglas Gilbert <dgilbert@interlog.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>
Subject: [PATCH 4.14 04/53] scsi: sg: mitigate read/write abuse
Date: Tue, 10 Jul 2018 20:24:40 +0200 [thread overview]
Message-ID: <20180710182459.073385200@linuxfoundation.org> (raw)
In-Reply-To: <20180710182458.736721865@linuxfoundation.org>
4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jann Horn <jannh@google.com>
commit 26b5b874aff5659a7e26e5b1997e3df2c41fa7fd upstream.
As Al Viro noted in commit 128394eff343 ("sg_write()/bsg_write() is not fit
to be called under KERNEL_DS"), sg improperly accesses userspace memory
outside the provided buffer, permitting kernel memory corruption via
splice(). But it doesn't just do it on ->write(), also on ->read().
As a band-aid, make sure that the ->read() and ->write() handlers can not
be called in weird contexts (kernel context or credentials different from
file opener), like for ib_safe_file_access().
If someone needs to use these interfaces from different security contexts,
a new interface should be written that goes through the ->ioctl() handler.
I've mostly copypasted ib_safe_file_access() over as sg_safe_file_access()
because I couldn't find a good common header - please tell me if you know a
better way.
[mkp: s/_safe_/_check_/]
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: <stable@vger.kernel.org>
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/scsi/sg.c | 42 ++++++++++++++++++++++++++++++++++++++++--
1 file changed, 40 insertions(+), 2 deletions(-)
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -51,6 +51,7 @@ static int sg_version_num = 30536; /* 2
#include <linux/atomic.h>
#include <linux/ratelimit.h>
#include <linux/uio.h>
+#include <linux/cred.h> /* for sg_check_file_access() */
#include "scsi.h"
#include <scsi/scsi_dbg.h>
@@ -210,6 +211,33 @@ static void sg_device_destroy(struct kre
sdev_prefix_printk(prefix, (sdp)->device, \
(sdp)->disk->disk_name, fmt, ##a)
+/*
+ * The SCSI interfaces that use read() and write() as an asynchronous variant of
+ * ioctl(..., SG_IO, ...) are fundamentally unsafe, since there are lots of ways
+ * to trigger read() and write() calls from various contexts with elevated
+ * privileges. This can lead to kernel memory corruption (e.g. if these
+ * interfaces are called through splice()) and privilege escalation inside
+ * userspace (e.g. if a process with access to such a device passes a file
+ * descriptor to a SUID binary as stdin/stdout/stderr).
+ *
+ * This function provides protection for the legacy API by restricting the
+ * calling context.
+ */
+static int sg_check_file_access(struct file *filp, const char *caller)
+{
+ if (filp->f_cred != current_real_cred()) {
+ pr_err_once("%s: process %d (%s) changed security contexts after opening file descriptor, this is not allowed.\n",
+ caller, task_tgid_vnr(current), current->comm);
+ return -EPERM;
+ }
+ if (uaccess_kernel()) {
+ pr_err_once("%s: process %d (%s) called from kernel context, this is not allowed.\n",
+ caller, task_tgid_vnr(current), current->comm);
+ return -EACCES;
+ }
+ return 0;
+}
+
static int sg_allow_access(struct file *filp, unsigned char *cmd)
{
struct sg_fd *sfp = filp->private_data;
@@ -394,6 +422,14 @@ sg_read(struct file *filp, char __user *
struct sg_header *old_hdr = NULL;
int retval = 0;
+ /*
+ * This could cause a response to be stranded. Close the associated
+ * file descriptor to free up any resources being held.
+ */
+ retval = sg_check_file_access(filp, __func__);
+ if (retval)
+ return retval;
+
if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
return -ENXIO;
SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp,
@@ -581,9 +617,11 @@ sg_write(struct file *filp, const char _
struct sg_header old_hdr;
sg_io_hdr_t *hp;
unsigned char cmnd[SG_MAX_CDB_SIZE];
+ int retval;
- if (unlikely(uaccess_kernel()))
- return -EINVAL;
+ retval = sg_check_file_access(filp, __func__);
+ if (retval)
+ return retval;
if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
return -ENXIO;
next prev parent reply other threads:[~2018-07-10 18:44 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-10 18:24 [PATCH 4.14 00/53] 4.14.55-stable review Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 01/53] userfaultfd: hugetlbfs: fix userfaultfd_huge_must_wait() pte access Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 02/53] mm: hugetlb: yield when prepping struct pages Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 03/53] tracing: Fix missing return symbol in function_graph output Greg Kroah-Hartman
2018-07-10 18:24 ` Greg Kroah-Hartman [this message]
2018-07-10 18:24 ` [PATCH 4.14 05/53] scsi: target: Fix truncated PR-in ReadKeys response Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 06/53] s390: Correct register corruption in critical section cleanup Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 07/53] drbd: fix access after free Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 08/53] vfio: Use get_user_pages_longterm correctly Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 09/53] cifs: Fix use after free of a mid_q_entry Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 10/53] cifs: Fix memory leak in smb2_set_ea() Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 11/53] cifs: Fix infinite loop when using hard mount option Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 12/53] cifs: Fix slab-out-of-bounds in send_set_info() on SMB2 ACE setting Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 13/53] drm: Use kvzalloc for allocating blob property memory Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 14/53] drm/udl: fix display corruption of the last line Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 15/53] jbd2: dont mark block as modified if the handle is out of credits Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 16/53] ext4: add corruption check in ext4_xattr_set_entry() Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 17/53] ext4: always verify the magic number in xattr blocks Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 18/53] ext4: make sure bitmaps and the inode table dont overlap with bg descriptors Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 19/53] ext4: always check block group bounds in ext4_init_block_bitmap() Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 20/53] ext4: only look at the bg_flags field if it is valid Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 21/53] ext4: verify the depth of extent tree in ext4_find_extent() Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 22/53] ext4: include the illegal physical block in the bad map ext4_error msg Greg Kroah-Hartman
2018-07-10 18:24 ` [PATCH 4.14 23/53] ext4: clear i_data in ext4_inode_info when removing inline data Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 24/53] ext4: never move the system.data xattr out of the inode body Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 25/53] ext4: avoid running out of journal credits when appending to an inline file Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 26/53] ext4: add more inode number paranoia checks Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 27/53] ext4: add more mount time checks of the superblock Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 28/53] ext4: check superblock mapped prior to committing Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 29/53] block: factor out __blkdev_issue_zero_pages() Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 30/53] block: cope with WRITE ZEROES failing in blkdev_issue_zeroout() Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 31/53] HID: i2c-hid: Fix "incomplete report" noise Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 32/53] HID: hiddev: fix potential Spectre v1 Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 33/53] HID: debug: check length before copy_to_user() Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 34/53] irq/core: Fix boot crash when the irqaffinity= boot parameter is passed on CPUMASK_OFFSTACK=y kernels(v1) Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 35/53] mm: hwpoison: disable memory error handling on 1GB hugepage Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 36/53] media: vb2: core: Finish buffers at the end of the stream Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 37/53] f2fs: truncate preallocated blocks in error case Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 38/53] [PATCH] Revert "dpaa_eth: fix error in dpaa_remove()" Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 39/53] Kbuild: fix # escaping in .cmd files for future Make Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 40/53] media: cx25840: Use subdev host data for PLL override Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 41/53] mtd: rawnand: mxc: set spare area size register explicitly Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 42/53] fs: allow per-device dax status checking for filesystems Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 43/53] dax: change bdev_dax_supported() to support boolean returns Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 44/53] dax: check for QUEUE_FLAG_DAX in bdev_dax_supported() Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 45/53] dm: set QUEUE_FLAG_DAX accordingly in dm_table_set_restrictions() Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 46/53] dm: prevent DAX mounts if not supported Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 47/53] mtd: cfi_cmdset_0002: Change definition naming to retry write operation Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 48/53] mtd: cfi_cmdset_0002: Change erase functions to retry for error Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 49/53] mtd: cfi_cmdset_0002: Change erase functions to check chip good only Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 50/53] netfilter: nf_log: dont hold nf_log_mutex during user access Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 51/53] staging: comedi: quatech_daqp_cs: fix no-op loop daqp_ao_insn_write() Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 52/53] sched, tracing: Fix trace_sched_pi_setprio() for deboosting Greg Kroah-Hartman
2018-07-10 18:25 ` [PATCH 4.14 53/53] Revert mm/vmstat.c: fix vmstat_update() preemption BUG Greg Kroah-Hartman
2018-07-11 13:05 ` [PATCH 4.14 00/53] 4.14.55-stable review Naresh Kamboju
2018-07-11 13:41 ` Guenter Roeck
2018-07-11 15:20 ` Shuah Khan
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