linux.git, branch v3.16.48

Linux 3.16.48

2017-09-15T17:30:20+00:00

Sanitize 'move_pages()' permission checks

2017-09-15T17:30:18+00:00

commit 197e7e521384a23b9e585178f3f11c9fa08274b9 upstream.

The 'move_paghes()' system call was introduced long long ago with the
same permission checks as for sending a signal (except using
CAP_SYS_NICE instead of CAP_SYS_KILL for the overriding capability).

That turns out to not be a great choice - while the system call really
only moves physical page allocations around (and you need other
capabilities to do a lot of it), you can check the return value to map
out some the virtual address choices and defeat ASLR of a binary that
still shares your uid.

So change the access checks to the more common 'ptrace_may_access()'
model instead.

This tightens the access checks for the uid, and also effectively
changes the CAP_SYS_NICE check to CAP_SYS_PTRACE, but it's unlikely that
anybody really _uses_ this legacy system call any more (we hav ebetter
NUMA placement models these days), so I expect nobody to notice.

Famous last words.

Reported-by: Otto Ebeling 
Acked-by: Eric W. Biederman 
Cc: Willy Tarreau 
Signed-off-by: Linus Torvalds 
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings

tcp: initialize rcv_mss to TCP_MIN_MSS instead of 0

2017-09-15T17:30:18+00:00

commit 499350a5a6e7512d9ed369ed63a4244b6536f4f8 upstream.

When tcp_disconnect() is called, inet_csk_delack_init() sets
icsk->icsk_ack.rcv_mss to 0.
This could potentially cause tcp_recvmsg() => tcp_cleanup_rbuf() =>
__tcp_select_window() call path to have division by 0 issue.
So this patch initializes rcv_mss to TCP_MIN_MSS instead of 0.

Reported-by: Andrey Konovalov  
Signed-off-by: Wei Wang 
Signed-off-by: Eric Dumazet 
Signed-off-by: Neal Cardwell 
Signed-off-by: Yuchung Cheng 
Signed-off-by: David S. Miller 
Signed-off-by: Ben Hutchings

xen: fix bio vec merging

2017-09-15T17:30:18+00:00

commit 462cdace790ac2ed6aad1b19c9c0af0143b6aab0 upstream.

The current test for bio vec merging is not fully accurate and can be
tricked into merging bios when certain grant combinations are used.
The result of these malicious bio merges is a bio that extends past
the memory page used by any of the originating bios.

Take into account the following scenario, where a guest creates two
grant references that point to the same mfn, ie: grant 1 -> mfn A,
grant 2 -> mfn A.

These references are then used in a PV block request, and mapped by
the backend domain, thus obtaining two different pfns that point to
the same mfn, pfn B -> mfn A, pfn C -> mfn A.

If those grants happen to be used in two consecutive sectors of a disk
IO operation becoming two different bios in the backend domain, the
checks in xen_biovec_phys_mergeable will succeed, because bfn1 == bfn2
(they both point to the same mfn). However due to the bio merging,
the backend domain will end up with a bio that expands past mfn A into
mfn A + 1.

Fix this by making sure the check in xen_biovec_phys_mergeable takes
into account the offset and the length of the bio, this basically
replicates whats done in __BIOVEC_PHYS_MERGEABLE using mfns (bus
addresses). While there also remove the usage of
__BIOVEC_PHYS_MERGEABLE, since that's already checked by the callers
of xen_biovec_phys_mergeable.

Reported-by: "Jan H. Schönherr" 
Signed-off-by: Roger Pau Monné 
Reviewed-by: Juergen Gross 
Signed-off-by: Konrad Rzeszutek Wilk 
[bwh: Backported to 3.16:
 - s/bfn/mfn/g
 - Adjust context]
Signed-off-by: Ben Hutchings

xfrm: policy: check policy direction value

2017-09-15T17:30:18+00:00

commit 7bab09631c2a303f87a7eb7e3d69e888673b9b7e upstream.

The 'dir' parameter in xfrm_migrate() is a user-controlled byte which is used
as an array index. This can lead to an out-of-bound access, kernel lockup and
DoS. Add a check for the 'dir' value.

This fixes CVE-2017-11600.

References: https://bugzilla.redhat.com/show_bug.cgi?id=1474928
Fixes: 80c9abaabf42 ("[XFRM]: Extension for dynamic update of endpoint address(es)")
Reported-by: "bo Zhang" 
Signed-off-by: Vladis Dronov 
Signed-off-by: Steffen Klassert 
Signed-off-by: Ben Hutchings

brcmfmac: fix possible buffer overflow in brcmf_cfg80211_mgmt_tx()

2017-09-15T17:30:18+00:00

commit 8f44c9a41386729fea410e688959ddaa9d51be7c upstream.

The lower level nl80211 code in cfg80211 ensures that "len" is between
25 and NL80211_ATTR_FRAME (2304).  We subtract DOT11_MGMT_HDR_LEN (24) from
"len" so thats's max of 2280.  However, the action_frame->data[] buffer is
only BRCMF_FIL_ACTION_FRAME_SIZE (1800) bytes long so this memcpy() can
overflow.

	memcpy(action_frame->data, &buf[DOT11_MGMT_HDR_LEN],
	       le16_to_cpu(action_frame->len));

Fixes: 18e2f61db3b70 ("brcmfmac: P2P action frame tx.")
Reported-by: "freenerguo(郭大兴)" 
Signed-off-by: Arend van Spriel 
Signed-off-by: David S. Miller 
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings

ptrace: use fsuid, fsgid, effective creds for fs access checks

2017-09-15T17:30:17+00:00

commit caaee6234d05a58c5b4d05e7bf766131b810a657 upstream.

By checking the effective credentials instead of the real UID / permitted
capabilities, ensure that the calling process actually intended to use its
credentials.

To ensure that all ptrace checks use the correct caller credentials (e.g.
in case out-of-tree code or newly added code omits the PTRACE_MODE_*CREDS
flag), use two new flags and require one of them to be set.

The problem was that when a privileged task had temporarily dropped its
privileges, e.g.  by calling setreuid(0, user_uid), with the intent to
perform following syscalls with the credentials of a user, it still passed
ptrace access checks that the user would not be able to pass.

While an attacker should not be able to convince the privileged task to
perform a ptrace() syscall, this is a problem because the ptrace access
check is reused for things in procfs.

In particular, the following somewhat interesting procfs entries only rely
on ptrace access checks:

 /proc/$pid/stat - uses the check for determining whether pointers
     should be visible, useful for bypassing ASLR
 /proc/$pid/maps - also useful for bypassing ASLR
 /proc/$pid/cwd - useful for gaining access to restricted
     directories that contain files with lax permissions, e.g. in
     this scenario:
     lrwxrwxrwx root root /proc/13020/cwd -> /root/foobar
     drwx------ root root /root
     drwxr-xr-x root root /root/foobar
     -rw-r--r-- root root /root/foobar/secret

Therefore, on a system where a root-owned mode 6755 binary changes its
effective credentials as described and then dumps a user-specified file,
this could be used by an attacker to reveal the memory layout of root's
processes or reveal the contents of files he is not allowed to access
(through /proc/$pid/cwd).

[akpm@linux-foundation.org: fix warning]
Signed-off-by: Jann Horn 
Acked-by: Kees Cook 
Cc: Casey Schaufler 
Cc: Oleg Nesterov 
Cc: Ingo Molnar 
Cc: James Morris 
Cc: "Serge E. Hallyn" 
Cc: Andy Shevchenko 
Cc: Andy Lutomirski 
Cc: Al Viro 
Cc: "Eric W. Biederman" 
Cc: Willy Tarreau 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
[bwh: Backported to 3.16:
 - Update mm_access() calls in fs/proc/task_{,no}mmu.c too
 - Adjust context]
Signed-off-by: Ben Hutchings

tracing/kprobes: Allow to create probe with a module name starting with a digit

2017-09-15T17:30:17+00:00

commit 9e52b32567126fe146f198971364f68d3bc5233f upstream.

Always try to parse an address, since kstrtoul() will safely fail when
given a symbol as input. If that fails (which will be the case for a
symbol), try to parse a symbol instead.

This allows creating a probe such as:

    p:probe/vlan_gro_receive 8021q:vlan_gro_receive+0

Which is necessary for this command to work:

    perf probe -m 8021q -a vlan_gro_receive

Link: http://lkml.kernel.org/r/fd72d666f45b114e2c5b9cf7e27b91de1ec966f1.1498122881.git.sd@queasysnail.net

Fixes: 413d37d1e ("tracing: Add kprobe-based event tracer")
Acked-by: Masami Hiramatsu 
Signed-off-by: Sabrina Dubroca 
Signed-off-by: Steven Rostedt (VMware) 
[bwh: Backported to 3.16: preserve the check that an addresses isn't used for
 a kretprobe]
Signed-off-by: Ben Hutchings

MIPS: Avoid accidental raw backtrace

2017-09-15T17:30:17+00:00

commit 854236363370995a609a10b03e35fd3dc5e9e4a1 upstream.

Since commit 81a76d7119f6 ("MIPS: Avoid using unwind_stack() with
usermode") show_backtrace() invokes the raw backtracer when
cp0_status & ST0_KSU indicates user mode to fix issues on EVA kernels
where user and kernel address spaces overlap.

However this is used by show_stack() which creates its own pt_regs on
the stack and leaves cp0_status uninitialised in most of the code paths.
This results in the non deterministic use of the raw back tracer
depending on the previous stack content.

show_stack() deals exclusively with kernel mode stacks anyway, so
explicitly initialise regs.cp0_status to KSU_KERNEL (i.e. 0) to ensure
we get a useful backtrace.

Fixes: 81a76d7119f6 ("MIPS: Avoid using unwind_stack() with usermode")
Signed-off-by: James Hogan 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16656/
Signed-off-by: Ralf Baechle 
Signed-off-by: Ben Hutchings

MIPS: Fix IRQ tracing & lockdep when rescheduling

2017-09-15T17:30:17+00:00

commit d8550860d910c6b7b70f830f59003b33daaa52c9 upstream.

When the scheduler sets TIF_NEED_RESCHED & we call into the scheduler
from arch/mips/kernel/entry.S we disable interrupts. This is true
regardless of whether we reach work_resched from syscall_exit_work,
resume_userspace or by looping after calling schedule(). Although we
disable interrupts in these paths we don't call trace_hardirqs_off()
before calling into C code which may acquire locks, and we therefore
leave lockdep with an inconsistent view of whether interrupts are
disabled or not when CONFIG_PROVE_LOCKING & CONFIG_DEBUG_LOCKDEP are
both enabled.

Without tracing this interrupt state lockdep will print warnings such
as the following once a task returns from a syscall via
syscall_exit_partial with TIF_NEED_RESCHED set:

[   49.927678] ------------[ cut here ]------------
[   49.934445] WARNING: CPU: 0 PID: 1 at kernel/locking/lockdep.c:3687 check_flags.part.41+0x1dc/0x1e8
[   49.946031] DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)
[   49.946355] CPU: 0 PID: 1 Comm: init Not tainted 4.10.0-00439-gc9fd5d362289-dirty #197
[   49.963505] Stack : 0000000000000000 ffffffff81bb5d6a 0000000000000006 ffffffff801ce9c4
[   49.974431]         0000000000000000 0000000000000000 0000000000000000 000000000000004a
[   49.985300]         ffffffff80b7e487 ffffffff80a24498 a8000000ff160000 ffffffff80ede8b8
[   49.996194]         0000000000000001 0000000000000000 0000000000000000 0000000077c8030c
[   50.007063]         000000007fd8a510 ffffffff801cd45c 0000000000000000 a8000000ff127c88
[   50.017945]         0000000000000000 ffffffff801cf928 0000000000000001 ffffffff80a24498
[   50.028827]         0000000000000000 0000000000000001 0000000000000000 0000000000000000
[   50.039688]         0000000000000000 a8000000ff127bd0 0000000000000000 ffffffff805509bc
[   50.050575]         00000000140084e0 0000000000000000 0000000000000000 0000000000040a00
[   50.061448]         0000000000000000 ffffffff8010e1b0 0000000000000000 ffffffff805509bc
[   50.072327]         ...
[   50.076087] Call Trace:
[   50.079869] [] show_stack+0x80/0xa8
[   50.086577] [] dump_stack+0x10c/0x190
[   50.093498] [] __warn+0xf0/0x108
[   50.099889] [] warn_slowpath_fmt+0x3c/0x48
[   50.107241] [] check_flags.part.41+0x1dc/0x1e8
[   50.114961] [] lock_is_held_type+0x8c/0xb0
[   50.122291] [] __schedule+0x8c0/0x10f8
[   50.129221] [] schedule+0x30/0x98
[   50.135659] [] work_resched+0x8/0x34
[   50.142397] ---[ end trace 0cb4f6ef5b99fe21 ]---
[   50.148405] possible reason: unannotated irqs-off.
[   50.154600] irq event stamp: 400463
[   50.159566] hardirqs last  enabled at (400463): [] _raw_spin_unlock_irqrestore+0x40/0xa8
[   50.171981] hardirqs last disabled at (400462): [] _raw_spin_lock_irqsave+0x30/0xb0
[   50.183897] softirqs last  enabled at (400450): [] __do_softirq+0x4ac/0x6a8
[   50.195015] softirqs last disabled at (400425): [] irq_exit+0x110/0x128

Fix this by using the TRACE_IRQS_OFF macro to call trace_hardirqs_off()
when CONFIG_TRACE_IRQFLAGS is enabled. This is done before invoking
schedule() following the work_resched label because:

 1) Interrupts are disabled regardless of the path we take to reach
    work_resched() & schedule().

 2) Performing the tracing here avoids the need to do it in paths which
    disable interrupts but don't call out to C code before hitting a
    path which uses the RESTORE_SOME macro that will call
    trace_hardirqs_on() or trace_hardirqs_off() as appropriate.

We call trace_hardirqs_on() using the TRACE_IRQS_ON macro before calling
syscall_trace_leave() for similar reasons, ensuring that lockdep has a
consistent view of state after we re-enable interrupts.

Signed-off-by: Paul Burton 
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/15385/
Signed-off-by: Ralf Baechle 
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings