[PATCH 4.4 08/69] KEYS: Fix short sprintf buffer in /proc/keys show function

From	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups	linux.kernel
Subject	[PATCH 4.4 08/69] KEYS: Fix short sprintf buffer in /proc/keys show function
Date	2016-11-09 12:00 +0100
Message-ID	<sByLL-6cP-5@gated-at.bofh.it> (permalink)
References	<sByC5-69v-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Howells <dhowells@redhat.com>

commit 03dab869b7b239c4e013ec82aea22e181e441cfc upstream.

This fixes CVE-2016-7042.

Fix a short sprintf buffer in proc_keys_show().  If the gcc stack protector
is turned on, this can cause a panic due to stack corruption.

The problem is that xbuf[] is not big enough to hold a 64-bit timeout
rendered as weeks:

	(gdb) p 0xffffffffffffffffULL/(60*60*24*7)
	$2 = 30500568904943

That's 14 chars plus NUL, not 11 chars plus NUL.

Expand the buffer to 16 chars.

I think the unpatched code apparently works if the stack-protector is not
enabled because on a 32-bit machine the buffer won't be overflowed and on a
64-bit machine there's a 64-bit aligned pointer at one side and an int that
isn't checked again on the other side.

The panic incurred looks something like:

Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffffff81352ebe
CPU: 0 PID: 1692 Comm: reproducer Not tainted 4.7.2-201.fc24.x86_64 #1
Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
 0000000000000086 00000000fbbd2679 ffff8800a044bc00 ffffffff813d941f
 ffffffff81a28d58 ffff8800a044bc98 ffff8800a044bc88 ffffffff811b2cb6
 ffff880000000010 ffff8800a044bc98 ffff8800a044bc30 00000000fbbd2679
Call Trace:
 [<ffffffff813d941f>] dump_stack+0x63/0x84
 [<ffffffff811b2cb6>] panic+0xde/0x22a
 [<ffffffff81352ebe>] ? proc_keys_show+0x3ce/0x3d0
 [<ffffffff8109f7f9>] __stack_chk_fail+0x19/0x30
 [<ffffffff81352ebe>] proc_keys_show+0x3ce/0x3d0
 [<ffffffff81350410>] ? key_validate+0x50/0x50
 [<ffffffff8134db30>] ? key_default_cmp+0x20/0x20
 [<ffffffff8126b31c>] seq_read+0x2cc/0x390
 [<ffffffff812b6b12>] proc_reg_read+0x42/0x70
 [<ffffffff81244fc7>] __vfs_read+0x37/0x150
 [<ffffffff81357020>] ? security_file_permission+0xa0/0xc0
 [<ffffffff81246156>] vfs_read+0x96/0x130
 [<ffffffff81247635>] SyS_read+0x55/0xc0
 [<ffffffff817eb872>] entry_SYSCALL_64_fastpath+0x1a/0xa4

Reported-by: Ondrej Kozina <okozina@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Ondrej Kozina <okozina@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 security/keys/proc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/security/keys/proc.c
+++ b/security/keys/proc.c
@@ -181,7 +181,7 @@ static int proc_keys_show(struct seq_fil
 	struct timespec now;
 	unsigned long timo;
 	key_ref_t key_ref, skey_ref;
-	char xbuf[12];
+	char xbuf[16];
 	int rc;
 
 	struct keyring_search_context ctx = {

Thread

[PATCH 4.4 00/69] 4.4.31-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 11:50 +0100
  [PATCH 4.4 23/69] USB: serial: ftdi_sio: add support for Infineon TriBoard TC2X7 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 11:50 +0100
  [PATCH 4.4 27/69] Fix potential infoleak in older kernels Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 11:50 +0100
  [PATCH 4.4 32/69] USB: serial: cp210x: fix tiocmget error handling Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 11:50 +0100
  [PATCH 4.4 04/69] h8300: fix syscall restarting Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 11:50 +0100
  [PATCH 4.4 01/69] i2c: xgene: Avoid dma_buffer overrun Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 11:50 +0100
  [PATCH 4.4 19/69] ubifs: Fix regression in ubifs_readdir() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 11:50 +0100
  [PATCH 4.4 29/69] hv: do not lose pending heartbeat vmbus packets Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 11:50 +0100
  [PATCH 4.4 31/69] tty: limit terminal size to 4M chars Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 11:50 +0100
  [PATCH 4.4 11/69] ALSA: hda - Raise AZX_DCAPS_RIRB_DELAY handling into top drivers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 11:50 +0100
  [PATCH 4.4 06/69] mm/list_lru.c: avoid error-path NULL pointer deref Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 11:50 +0100
  [PATCH 4.4 20/69] mei: txe: dont clean an unprocessed interrupt cause. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 11:50 +0100
  [PATCH 4.4 22/69] USB: serial: fix potential NULL-dereference at probe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 11:50 +0100
  [PATCH 4.4 18/69] ubifs: Abort readdir upon error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 11:50 +0100
  [PATCH 4.4 26/69] GenWQE: Fix bad page access during abort of resource allocation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 11:50 +0100
  [PATCH 4.4 08/69] KEYS: Fix short sprintf buffer in /proc/keys show function Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:00 +0100
  [PATCH 4.4 02/69] i2c: core: fix NULL pointer dereference under race condition Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:00 +0100
  [PATCH 4.4 07/69] mm: memcontrol: do not recurse in direct reclaim Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:00 +0100
  [PATCH 4.4 67/69] kvm: x86: Check memopp before dereference (CVE-2016-8630) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:10 +0100
  [PATCH 4.4 60/69] cgroup: avoid false positive gcc-6 warning Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:10 +0100
  [PATCH 4.4 37/69] parisc: Ensure consistent state when switching to kernel stack at syscall entry Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:10 +0100
  [PATCH 4.4 46/69] scsi: scsi_debug: Fix memory leak if LBP enabled and module is unloaded Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:10 +0100
  [PATCH 4.4 39/69] virtio: console: Unlock vqs while freeing buffers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:10 +0100
  [PATCH 4.4 47/69] scsi: arcmsr: Send SYNCHRONIZE_CACHE command to firmware Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:10 +0100
  [PATCH 4.4 65/69] usb: dwc3: Fix size used in dma_free_coherent() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:10 +0100
  [PATCH 4.4 54/69] perf build: Fix traceevent plugins build race Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:10 +0100
  [PATCH 4.4 38/69] virtio_ring: Make interrupt suppression spec compliant Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:10 +0100
  [PATCH 4.4 57/69] ARM: 8584/1: floppy: avoid gcc-6 warning Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:10 +0100
  [PATCH 4.4 51/69] drm/radeon/si_dpm: workaround for SI kickers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:10 +0100
  [PATCH 4.4 64/69] pwm: Unexport children before chip removal Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:10 +0100
  [PATCH 4.4 36/69] ovl: fsync after copy-up Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:10 +0100
  [PATCH 4.4 42/69] firewire: net: guard against rx buffer overflows Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:10 +0100
  [PATCH 4.4 68/69] ubi: fastmap: Fix add_vol() return value test in ubi_attach_fastmap() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:40 +0100
  [PATCH 4.4 44/69] mac80211: discard multicast and 4-addr A-MSDUs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:40 +0100
  [PATCH 4.4 43/69] firewire: net: fix fragmented datagram_size off-by-one Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:40 +0100
  [PATCH 4.4 45/69] scsi: megaraid_sas: Fix data integrity failure for JBOD (passthrough) devices Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:40 +0100
  [PATCH 4.4 69/69] HID: usbhid: add ATEN CS962 to list of quirky devices Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:40 +0100
  [PATCH 4.4 50/69] drm/radeon/si_dpm: Limit clocks on HD86xx part Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:50 +0100
  [PATCH 4.4 58/69] mm/cma: silence warnings due to max() usage Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:50 +0100
  [PATCH 4.4 59/69] drm/exynos: fix error handling in exynos_drm_subdrv_open Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:50 +0100
  [PATCH 4.4 41/69] Input: i8042 - add XMG C504 to keyboard reset table Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:50 +0100
  [PATCH 4.4 48/69] mmc: dw_mmc-pltfm: fix the potential NULL pointer dereference Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:50 +0100
  [PATCH 4.4 63/69] UBI: fastmap: scrub PEB when bitflips are detected in a free PEB EC header Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:50 +0100
  [PATCH 4.4 55/69] x86/xen: fix upper bound of pmd loop in xen_cleanhighmap() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:50 +0100
  [PATCH 4.4 56/69] powerpc/ptrace: Fix out of bounds array access warning Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:50 +0100
  [PATCH 4.4 40/69] dm mirror: fix read error on recovery after default leg failure Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:50 +0100
  [PATCH 4.4 61/69] smc91x: avoid self-comparison warning Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-09 12:50 +0100
  Re: [PATCH 4.4 00/69] 4.4.31-stable review Shuah Khan <shuah.kh@samsung.com> - 2016-11-09 19:30 +0100
  Re: [PATCH 4.4 00/69] 4.4.31-stable review Guenter Roeck <linux@roeck-us.net> - 2016-11-09 20:40 +0100

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