linux-stable.git/fs/proc, branch linux-2.6.35.y

proc: restrict access to /proc/PID/io

2011-08-01T20:54:59+00:00

[ upstream commit 1d1221f375c94ef961ba8574ac4f85c8870ddd51 ]

/proc/PID/io may be used for gathering private information.  E.g.  for
openssh and vsftpd daemons wchars/rchars may be used to learn the
precise password length.  Restrict it to processes being able to ptrace
the target process.

ptrace_may_access() is needed to prevent keeping open file descriptor of
"io" file, executing setuid binary and gathering io information of the
setuid'ed process.

Said to be CVE-2011-2495

Signed-off-by: Vasiliy Kulikov 
Signed-off-by: Linus Torvalds 
Signed-off-by: Andi Kleen

proc: do proper range check on readdir offset

2011-04-28T15:21:08+00:00

commit d8bdc59f215e62098bc5b4256fd9928bf27053a1 upstream.

Rather than pass in some random truncated offset to the pid-related
functions, check that the offset is in range up-front.

This is just cleanup, the previous commit fixed the real problem.

Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Andi Kleen

proc: protect mm start_code/end_code in /proc/pid/stat

2011-03-31T18:58:45+00:00

commit 5883f57ca0008ffc93e09cbb9847a1928e50c6f3 upstream.

While mm->start_stack was protected from cross-uid viewing (commit
f83ce3e6b02d5 ("proc: avoid information leaks to non-privileged
processes")), the start_code and end_code values were not.  This would
allow the text location of a PIE binary to leak, defeating ASLR.

Note that the value "1" is used instead of "0" for a protected value since
"ps", "killall", and likely other readers of /proc/pid/stat, take
start_code of "0" to mean a kernel thread and will misbehave.  Thanks to
Brad Spengler for pointing this out.

Addresses CVE-2011-0726

Signed-off-by: Kees Cook 
Signed-off-by: Andi Kleen 
Cc: Alexey Dobriyan 
Cc: David Howells 
Cc: Eugene Teo 
Cc: Martin Schwidefsky 
Cc: Brad Spengler 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

procfs: fix /proc//maps heap check

2011-03-31T18:58:45+00:00

commit 0db0c01b53a1a421513f91573241aabafb87802a upstream.

The current code fails to print the "[heap]" marking if the heap is split
into multiple mappings.

Fix the check so that the marking is displayed in all possible cases:
	1. vma matches exactly the heap
	2. the heap vma is merged e.g. with bss
	3. the heap vma is splitted e.g. due to locked pages

Test cases. In all cases, the process should have mapping(s) with
[heap] marking:

	(1) vma matches exactly the heap

	#include 
	#include 
	#include 

	int main (void)
	{
		if (sbrk(4096) != (void *)-1) {
			printf("check /proc/%d/maps\n", (int)getpid());
			while (1)
				sleep(1);
		}
		return 0;
	}

	# ./test1
	check /proc/553/maps
	[1] + Stopped                    ./test1
	# cat /proc/553/maps | head -4
	00008000-00009000 r-xp 00000000 01:00 3113640    /test1
	00010000-00011000 rw-p 00000000 01:00 3113640    /test1
	00011000-00012000 rw-p 00000000 00:00 0          [heap]
	4006f000-40070000 rw-p 00000000 00:00 0

	(2) the heap vma is merged

	#include 
	#include 
	#include 

	char foo[4096] = "foo";
	char bar[4096];

	int main (void)
	{
		if (sbrk(4096) != (void *)-1) {
			printf("check /proc/%d/maps\n", (int)getpid());
			while (1)
				sleep(1);
		}
		return 0;
	}

	# ./test2
	check /proc/556/maps
	[2] + Stopped                    ./test2
	# cat /proc/556/maps | head -4
	00008000-00009000 r-xp 00000000 01:00 3116312    /test2
	00010000-00012000 rw-p 00000000 01:00 3116312    /test2
	00012000-00014000 rw-p 00000000 00:00 0          [heap]
	4004a000-4004b000 rw-p 00000000 00:00 0

	(3) the heap vma is splitted (this fails without the patch)

	#include 
	#include 
	#include 
	#include 

	int main (void)
	{
		if ((sbrk(4096) != (void *)-1) && !mlockall(MCL_FUTURE) &&
		    (sbrk(4096) != (void *)-1)) {
			printf("check /proc/%d/maps\n", (int)getpid());
			while (1)
				sleep(1);
		}
		return 0;
	}

	# ./test3
	check /proc/559/maps
	[1] + Stopped                    ./test3
	# cat /proc/559/maps|head -4
	00008000-00009000 r-xp 00000000 01:00 3119108    /test3
	00010000-00011000 rw-p 00000000 01:00 3119108    /test3
	00011000-00012000 rw-p 00000000 00:00 0          [heap]
	00012000-00013000 rw-p 00000000 00:00 0          [heap]

It looks like the bug has been there forever, and since it only results in
some information missing from a procfile, it does not fulfil the -stable
"critical issue" criteria.

Signed-off-by: Aaro Koskinen 
Signed-off-by: Andi Kleen 
Reviewed-by: KOSAKI Motohiro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

s390: remove task_show_regs

2011-03-31T18:58:07+00:00

commit 261cd298a8c363d7985e3482946edb4bfedacf98 upstream.

task_show_regs used to be a debugging aid in the early bringup days
of Linux on s390. /proc//status is a world readable file, it
is not a good idea to show the registers of a process. The only
correct fix is to remove task_show_regs.

Reported-by: Al Viro 
Signed-off-by: Martin Schwidefsky 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Andi Kleen

mm: Move vma_stack_continue into mm.h

2010-10-29T04:51:47+00:00

commit 39aa3cb3e8250db9188a6f1e3fb62ffa1a717678 upstream.

So it can be used by all that need to check for that.

Signed-off-by: Stefan Bader 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

/proc/vmcore: fix seeking

2010-09-27T00:18:28+00:00

commit c227e69028473c7c7994a9b0a2cc0034f3f7e0fe upstream.

Commit 73296bc611 ("procfs: Use generic_file_llseek in /proc/vmcore")
broke seeking on /proc/vmcore.  This changes it back to use default_llseek
in order to restore the original behaviour.

The problem with generic_file_llseek is that it only allows seeks up to
inode->i_sb->s_maxbytes, which is zero on procfs and some other virtual
file systems.  We should merge generic_file_llseek and default_llseek some
day and clean this up in a proper way, but for 2.6.35/36, reverting vmcore
is the safer solution.

Signed-off-by: Arnd Bergmann 
Cc: Frederic Weisbecker 
Reported-by: CAI Qian 
Tested-by: CAI Qian 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: fix up some user-visible effects of the stack guard page

2010-08-20T18:55:38+00:00

commit d7824370e26325c881b665350ce64fb0a4fde24a upstream.

This commit makes the stack guard page somewhat less visible to user
space. It does this by:

 - not showing the guard page in /proc//maps

   It looks like lvm-tools will actually read /proc/self/maps to figure
   out where all its mappings are, and effectively do a specialized
   "mlockall()" in user space.  By not showing the guard page as part of
   the mapping (by just adding PAGE_SIZE to the start for grows-up
   pages), lvm-tools ends up not being aware of it.

 - by also teaching the _real_ mlock() functionality not to try to lock
   the guard page.

   That would just expand the mapping down to create a new guard page,
   so there really is no point in trying to lock it in place.

It would perhaps be nice to show the guard page specially in
/proc//maps (or at least mark grow-down segments some way), but
let's not open ourselves up to more breakage by user space from programs
that depends on the exact deails of the 'maps' file.

Special thanks to Henrique de Moraes Holschuh for diving into lvm-tools
source code to see what was going on with the whole new warning.

Reported-and-tested-by: François Valenduc 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

CRED: Fix get_task_cred() and task_state() to not resurrect dead credentials

2010-07-29T22:16:17+00:00

It's possible for get_task_cred() as it currently stands to 'corrupt' a set of
credentials by incrementing their usage count after their replacement by the
task being accessed.

What happens is that get_task_cred() can race with commit_creds():

	TASK_1			TASK_2			RCU_CLEANER
	-->get_task_cred(TASK_2)
	rcu_read_lock()
	__cred = __task_cred(TASK_2)
				-->commit_creds()
				old_cred = TASK_2->real_cred
				TASK_2->real_cred = ...
				put_cred(old_cred)
				  call_rcu(old_cred)
		[__cred->usage == 0]
	get_cred(__cred)
		[__cred->usage == 1]
	rcu_read_unlock()
							-->put_cred_rcu()
							[__cred->usage == 1]
							panic()

However, since a tasks credentials are generally not changed very often, we can
reasonably make use of a loop involving reading the creds pointer and using
atomic_inc_not_zero() to attempt to increment it if it hasn't already hit zero.

If successful, we can safely return the credentials in the knowledge that, even
if the task we're accessing has released them, they haven't gone to the RCU
cleanup code.

We then change task_state() in procfs to use get_task_cred() rather than
calling get_cred() on the result of __task_cred(), as that suffers from the
same problem.

Without this change, a BUG_ON in __put_cred() or in put_cred_rcu() can be
tripped when it is noticed that the usage count is not zero as it ought to be,
for example:

kernel BUG at kernel/cred.c:168!
invalid opcode: 0000 [#1] SMP
last sysfs file: /sys/kernel/mm/ksm/run
CPU 0
Pid: 2436, comm: master Not tainted 2.6.33.3-85.fc13.x86_64 #1 0HR330/OptiPlex
745
RIP: 0010:[]  [] __put_cred+0xc/0x45
RSP: 0018:ffff88019e7e9eb8  EFLAGS: 00010202
RAX: 0000000000000001 RBX: ffff880161514480 RCX: 00000000ffffffff
RDX: 00000000ffffffff RSI: ffff880140c690c0 RDI: ffff880140c690c0
RBP: ffff88019e7e9eb8 R08: 00000000000000d0 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000040 R12: ffff880140c690c0
R13: ffff88019e77aea0 R14: 00007fff336b0a5c R15: 0000000000000001
FS:  00007f12f50d97c0(0000) GS:ffff880007400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8f461bc000 CR3: 00000001b26ce000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process master (pid: 2436, threadinfo ffff88019e7e8000, task ffff88019e77aea0)
Stack:
 ffff88019e7e9ec8 ffffffff810698cd ffff88019e7e9ef8 ffffffff81069b45
<0> ffff880161514180 ffff880161514480 ffff880161514180 0000000000000000
<0> ffff88019e7e9f28 ffffffff8106aace 0000000000000001 0000000000000246
Call Trace:
 [] put_cred+0x13/0x15
 [] commit_creds+0x16b/0x175
 [] set_current_groups+0x47/0x4e
 [] sys_setgroups+0xf6/0x105
 [] system_call_fastpath+0x16/0x1b
Code: 48 8d 71 ff e8 7e 4e 15 00 85 c0 78 0b 8b 75 ec 48 89 df e8 ef 4a 15 00
48 83 c4 18 5b c9 c3 55 8b 07 8b 07 48 89 e5 85 c0 74 04 <0f> 0b eb fe 65 48 8b
04 25 00 cc 00 00 48 3b b8 58 04 00 00 75
RIP  [] __put_cred+0xc/0x45
 RSP 
---[ end trace df391256a100ebdd ]---

Signed-off-by: David Howells 
Acked-by: Jiri Olsa 
Signed-off-by: Linus Torvalds

nommu: add '[stack]' label to /proc/pid/maps output

2010-06-29T22:29:30+00:00

Add support to the NOMMU /proc/pid/maps file to show which mapping is the stack
of the original thread after execve.  This is largely based on the MMU code.
Subsidiary thread stacks are not indicated.

For FDPIC, we now get:

	root:/> cat /proc/self/maps
	02064000-02067ccc rw-p 0004d000 00:01 22         /bin/busybox
	0206e000-0206f35c rw-p 00006000 00:01 295        /lib/ld-uClibc.so.0
	025f0000-025f6f0c r-xs 00000000 00:01 295        /lib/ld-uClibc.so.0
	02680000-026ba6b0 r-xs 00000000 00:01 297        /lib/libc.so.0
	02700000-0274d384 r-xs 00000000 00:01 22         /bin/busybox
	02816000-02817000 rw-p 00000000 00:00 0
	02848000-0284c0d8 rw-p 00000000 00:00 0
	02860000-02880000 rw-p 00000000 00:00 0          [stack]

The semi-downside here is that for FLAT, we get:

	root:/> cat /proc/155/maps
	029f0000-029f9000 rwxp 00000000 00:00 0          [stack]

The reason being that FLAT combines a whole lot of stuff into one map
(including the stack).  But this isn't any worse than the current output
(which is nothing), so screw it.

Signed-off-by: Mike Frysinger 
Signed-off-by: David Howells 
Cc: Greg Ungerer 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds