Skip to content

L
linux
Switch branch/tag
  1. 09 Jan, 2015 6 commits
    • Andy Lutomirski's avatar
      x86_64, switch_to(): Load TLS descriptors before switching DS and ES · 1ea5aeec
      Andy Lutomirski authored 
      Otherwise, if buggy user code points DS or ES into the TLS
array, they would be corrupted after a context switch.

This also significantly improves the comments and documents some
gotchas in the code.

Before this patch, the both tests below failed.  With this
patch, the es test passes, although the gsbase test still fails.

 ----- begin es test -----

/*
 * Copyright (c) 2014 Andy Lutomirski
 * GPL v2
 */

static unsigned short GDT3(int idx)
{
	return (idx << 3) | 3;
}

static int create_tls(int idx, unsigned int base)
{
	struct user_desc desc = {
		.entry_number    = idx,
		.base_addr       = base,
		.limit           = 0xfffff,
		.seg_32bit       = 1,
		.contents        = 0, /* Data, grow-up */
		.read_exec_only  = 0,
		.limit_in_pages  = 1,
		.seg_not_present = 0,
		.useable         = 0,
	};

	if (syscall(SYS_set_thread_area, &desc) != 0)
		err(1, "set_thread_area");

	return desc.entry_number;
}

int main()
{
	int idx = create_tls(-1, 0);
	printf("Allocated GDT index %d\n", idx);

	unsigned short orig_es;
	asm volatile ("mov %%es,%0" : "=rm" (orig_es));

	int errors = 0;
	int total = 1000;
	for (int i = 0; i < total; i++) {
		asm volatile ("mov %0,%%es" : : "rm" (GDT3(idx)));
		usleep(100);

		unsigned short es;
		asm volatile ("mov %%es,%0" : "=rm" (es));
		asm volatile ("mov %0,%%es" : : "rm" (orig_es));
		if (es != GDT3(idx)) {
			if (errors == 0)
				printf("[FAIL]\tES changed from 0x%hx to 0x%hx\n",
				       GDT3(idx), es);
			errors++;
		}
	}

	if (errors) {
		printf("[FAIL]\tES was corrupted %d/%d times\n", errors, total);
		return 1;
	} else {
		printf("[OK]\tES was preserved\n");
		return 0;
	}
}

 ----- end es test -----

 ----- begin gsbase test -----

/*
 * gsbase.c, a gsbase test
 * Copyright (c) 2014 Andy Lutomirski
 * GPL v2
 */

static unsigned char *testptr, *testptr2;

static unsigned char read_gs_testvals(void)
{
	unsigned char ret;
	asm volatile ("movb %%gs:%1, %0" : "=r" (ret) : "m" (*testptr));
	return ret;
}

int main()
{
	int errors = 0;

	testptr = mmap((void *)0x200000000UL, 1, PROT_READ | PROT_WRITE,
		       MAP_PRIVATE | MAP_FIXED | MAP_ANONYMOUS, -1, 0);
	if (testptr == MAP_FAILED)
		err(1, "mmap");

	testptr2 = mmap((void *)0x300000000UL, 1, PROT_READ | PROT_WRITE,
		       MAP_PRIVATE | MAP_FIXED | MAP_ANONYMOUS, -1, 0);
	if (testptr2 == MAP_FAILED)
		err(1, "mmap");

	*testptr = 0;
	*testptr2 = 1;

	if (syscall(SYS_arch_prctl, ARCH_SET_GS,
		    (unsigned long)testptr2 - (unsigned long)testptr) != 0)
		err(1, "ARCH_SET_GS");

	usleep(100);

	if (read_gs_testvals() == 1) {
		printf("[OK]\tARCH_SET_GS worked\n");
	} else {
		printf("[FAIL]\tARCH_SET_GS failed\n");
		errors++;
	}

	asm volatile ("mov %0,%%gs" : : "r" (0));

	if (read_gs_testvals() == 0) {
		printf("[OK]\tWriting 0 to gs worked\n");
	} else {
		printf("[FAIL]\tWriting 0 to gs failed\n");
		errors++;
	}

	usleep(100);

	if (read_gs_testvals() == 0) {
		printf("[OK]\tgsbase is still zero\n");
	} else {
		printf("[FAIL]\tgsbase was corrupted\n");
		errors++;
	}

	return errors == 0 ? 0 : 1;
}

 ----- end gsbase test -----
Signed-off-by: default avatarAndy Lutomirski <luto@amacapital.net>
Cc: <stable@vger.kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/509d27c9fec78217691c3dad91cec87e1006b34a.1418075657.git.luto@amacapital.netSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>

(cherry picked from commit f647d7c1)
Signed-off-by: default avatarSasha Levin <sasha.levin@oracle.com>
      1ea5aeec
    • Andy Lutomirski's avatar
      x86/tls: Don't validate lm in set_thread_area() after all · cfa9801f
      Andy Lutomirski authored 
      It turns out that there's a lurking ABI issue.  GCC, when
compiling this in a 32-bit program:

struct user_desc desc = {
	.entry_number    = idx,
	.base_addr       = base,
	.limit           = 0xfffff,
	.seg_32bit       = 1,
	.contents        = 0, /* Data, grow-up */
	.read_exec_only  = 0,
	.limit_in_pages  = 1,
	.seg_not_present = 0,
	.useable         = 0,
};

will leave .lm uninitialized.  This means that anything in the
kernel that reads user_desc.lm for 32-bit tasks is unreliable.

Revert the .lm check in set_thread_area().  The value never did
anything in the first place.

Fixes: 0e58af4e ("x86/tls: Disallow unusual TLS segments")
Signed-off-by: default avatarAndy Lutomirski <luto@amacapital.net>
Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org # Only if 0e58af4e is backported
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/d7875b60e28c512f6a6fc0baf5714d58e7eaadbb.1418856405.git.luto@amacapital.netSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>

x86/tls: Disallow unusual TLS segments

Users have no business installing custom code segments into the
GDT, and segments that are not present but are otherwise valid
are a historical source of interesting attacks.

For completeness, block attempts to set the L bit.  (Prior to
this patch, the L bit would have been silently dropped.)

This is an ABI break.  I've checked glibc, musl, and Wine, and
none of them look like they'll have any trouble.

Note to stable maintainers: this is a hardening patch that fixes
no known bugs.  Given the possibility of ABI issues, this
probably shouldn't be backported quickly.
Signed-off-by: default avatarAndy Lutomirski <luto@amacapital.net>
Acked-by: default avatarH. Peter Anvin <hpa@zytor.com>
Cc: stable@vger.kernel.org # optional
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: security@kernel.org <security@kernel.org>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>

(cherry picked from commit 3fb2f423
0e58af4e)
Signed-off-by: default avatarSasha Levin <sasha.levin@oracle.com>
      cfa9801f
    • Andy Lutomirski's avatar
      x86/tls: Validate TLS entries to protect espfix · 8d8ed1e1
      Andy Lutomirski authored 
      Installing a 16-bit RW data segment into the GDT defeats espfix.
AFAICT this will not affect glibc, Wine, or dosemu at all.
Signed-off-by: default avatarAndy Lutomirski <luto@amacapital.net>
Acked-by: default avatarH. Peter Anvin <hpa@zytor.com>
Cc: stable@vger.kernel.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: security@kernel.org <security@kernel.org>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>

(cherry picked from commit 41bdc785)
Signed-off-by: default avatarSasha Levin <sasha.levin@oracle.com>
      8d8ed1e1
    • Jan Kara's avatar
      isofs: Fix infinite looping over CE entries · d1d8fb85
      Jan Kara authored 
      Rock Ridge extensions define so called Continuation Entries (CE) which
define where is further space with Rock Ridge data. Corrupted isofs
image can contain arbitrarily long chain of these, including a one
containing loop and thus causing kernel to end in an infinite loop when
traversing these entries.

Limit the traversal to 32 entries which should be more than enough space
to store all the Rock Ridge data.
Reported-by: default avatarP J P <ppandit@redhat.com>
CC: stable@vger.kernel.org
Signed-off-by: default avatarJan Kara <jack@suse.cz>

(cherry picked from commit f54e18f1)
Signed-off-by: default avatarSasha Levin <sasha.levin@oracle.com>
      d1d8fb85
    • Larry Finger's avatar
      rtlwifi: rtl8192ce: Fix missing interrupt ready flag · f26e1966
      Larry Finger authored 
      Proper operation with the rewritten PCI mini driver requires that a flag be set
when interrupts are enabled. This flag was missed.  This patch is one of three needed to
fix the kernel regression reported at https://bugzilla.kernel.org/show_bug.cgi?id=88951.
Signed-off-by: default avatarLarry Finger <Larry.Finger@lwfinger.net>
Reported-by: default avatarCatalin Iacob <iacobcatalin@gmail.com>
Tested-by: default avatarCatalin Iacob <iacobcatalin@gmail.com>
Cc: Catalin Iacob <iacobcatalin@gmail.com>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>

(cherry picked from commit 87141db0)
Signed-off-by: default avatarSasha Levin <sasha.levin@oracle.com>
      f26e1966
    • Larry Finger's avatar
      rtlwifi: rtl8192ce: Fix kernel crashes due to missing callback entry · 506910b6
      Larry Finger authored 
      In the major update of the rtlwifi-family of drivers, one of the callback entries
was missed, which leads to memory corruption. Unfortunately, this corruption
never caused a kernel oops, but showed up in other parts of the system.
This patch is one of three needed to fix the kernel regression reported at
https://bugzilla.kernel.org/show_bug.cgi?id=88951.
Signed-off-by: default avatarLarry Finger <Larry.Finger@lwfinger.net>
Reported-by: default avatarCatalin Iacob <iacobcatalin@gmail.com>
Tested-by: default avatarCatalin Iacob <iacobcatalin@gmail.com>
Cc: Catalin Iacob <iacobcatalin@gmail.com>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>

(cherry picked from commit f892914c)
Signed-off-by: default avatarSasha Levin <sasha.levin@oracle.com>
      506910b6
  3. 22 Dec, 2014 34 commits
GitLab Nexedi Edition | About GitLab | About Nexedi | 沪ICP备2021021310号-2 | 沪ICP备2021021310号-7