This fixes a Spectre-v1/L1TF vulnerability in picdev_write().
It replaces index computations based on the (attacked-controlled) port
number with constants through a minor refactoring.
Fixes: commit 85f455f7ddbe ("KVM: Add support for in-kernel PIC emulation")
Signed-off-by: Nick Finco <nifi(a)google.com>
Signed-off-by: Marios Pomonis <pomonis(a)google.com>
Reviewed-by: Andrew Honig <ahonig(a)google.com>
Cc: stable(a)vger.kernel.org
---
arch/x86/kvm/i8259.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
index 8b38bb4868a6..629a09ca9860 100644
--- a/arch/x86/kvm/i8259.c
+++ b/arch/x86/kvm/i8259.c
@@ -460,10 +460,14 @@ static int picdev_write(struct kvm_pic *s,
switch (addr) {
case 0x20:
case 0x21:
+ pic_lock(s);
+ pic_ioport_write(&s->pics[0], addr, data);
+ pic_unlock(s);
+ break;
case 0xa0:
case 0xa1:
pic_lock(s);
- pic_ioport_write(&s->pics[addr >> 7], addr, data);
+ pic_ioport_write(&s->pics[1], addr, data);
pic_unlock(s);
break;
case 0x4d0:
--
2.24.0.525.g8f36a354ae-goog
This is a note to let you know that I've just added the patch titled
chardev: Avoid potential use-after-free in 'chrdev_open()'
to my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-testing branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will be merged to the char-misc-next branch sometime soon,
after it passes testing, and the merge window is open.
If you have any questions about this process, please let me know.
>From 68faa679b8be1a74e6663c21c3a9d25d32f1c079 Mon Sep 17 00:00:00 2001
From: Will Deacon <will(a)kernel.org>
Date: Thu, 19 Dec 2019 12:02:03 +0000
Subject: chardev: Avoid potential use-after-free in 'chrdev_open()'
'chrdev_open()' calls 'cdev_get()' to obtain a reference to the
'struct cdev *' stashed in the 'i_cdev' field of the target inode
structure. If the pointer is NULL, then it is initialised lazily by
looking up the kobject in the 'cdev_map' and so the whole procedure is
protected by the 'cdev_lock' spinlock to serialise initialisation of
the shared pointer.
Unfortunately, it is possible for the initialising thread to fail *after*
installing the new pointer, for example if the subsequent '->open()' call
on the file fails. In this case, 'cdev_put()' is called, the reference
count on the kobject is dropped and, if nobody else has taken a reference,
the release function is called which finally clears 'inode->i_cdev' from
'cdev_purge()' before potentially freeing the object. The problem here
is that a racing thread can happily take the 'cdev_lock' and see the
non-NULL pointer in the inode, which can result in a refcount increment
from zero and a warning:
| ------------[ cut here ]------------
| refcount_t: addition on 0; use-after-free.
| WARNING: CPU: 2 PID: 6385 at lib/refcount.c:25 refcount_warn_saturate+0x6d/0xf0
| Modules linked in:
| CPU: 2 PID: 6385 Comm: repro Not tainted 5.5.0-rc2+ #22
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
| RIP: 0010:refcount_warn_saturate+0x6d/0xf0
| Code: 05 55 9a 15 01 01 e8 9d aa c8 ff 0f 0b c3 80 3d 45 9a 15 01 00 75 ce 48 c7 c7 00 9c 62 b3 c6 08
| RSP: 0018:ffffb524c1b9bc70 EFLAGS: 00010282
| RAX: 0000000000000000 RBX: ffff9e9da1f71390 RCX: 0000000000000000
| RDX: ffff9e9dbbd27618 RSI: ffff9e9dbbd18798 RDI: ffff9e9dbbd18798
| RBP: 0000000000000000 R08: 000000000000095f R09: 0000000000000039
| R10: 0000000000000000 R11: ffffb524c1b9bb20 R12: ffff9e9da1e8c700
| R13: ffffffffb25ee8b0 R14: 0000000000000000 R15: ffff9e9da1e8c700
| FS: 00007f3b87d26700(0000) GS:ffff9e9dbbd00000(0000) knlGS:0000000000000000
| CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
| CR2: 00007fc16909c000 CR3: 000000012df9c000 CR4: 00000000000006e0
| DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
| DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
| Call Trace:
| kobject_get+0x5c/0x60
| cdev_get+0x2b/0x60
| chrdev_open+0x55/0x220
| ? cdev_put.part.3+0x20/0x20
| do_dentry_open+0x13a/0x390
| path_openat+0x2c8/0x1470
| do_filp_open+0x93/0x100
| ? selinux_file_ioctl+0x17f/0x220
| do_sys_open+0x186/0x220
| do_syscall_64+0x48/0x150
| entry_SYSCALL_64_after_hwframe+0x44/0xa9
| RIP: 0033:0x7f3b87efcd0e
| Code: 89 54 24 08 e8 a3 f4 ff ff 8b 74 24 0c 48 8b 3c 24 41 89 c0 44 8b 54 24 08 b8 01 01 00 00 89 f4
| RSP: 002b:00007f3b87d259f0 EFLAGS: 00000293 ORIG_RAX: 0000000000000101
| RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f3b87efcd0e
| RDX: 0000000000000000 RSI: 00007f3b87d25a80 RDI: 00000000ffffff9c
| RBP: 00007f3b87d25e90 R08: 0000000000000000 R09: 0000000000000000
| R10: 0000000000000000 R11: 0000000000000293 R12: 00007ffe188f504e
| R13: 00007ffe188f504f R14: 00007f3b87d26700 R15: 0000000000000000
| ---[ end trace 24f53ca58db8180a ]---
Since 'cdev_get()' can already fail to obtain a reference, simply move
it over to use 'kobject_get_unless_zero()' instead of 'kobject_get()',
which will cause the racing thread to return -ENXIO if the initialising
thread fails unexpectedly.
Cc: Hillf Danton <hdanton(a)sina.com>
Cc: Andrew Morton <akpm(a)linux-foundation.org>
Cc: Al Viro <viro(a)zeniv.linux.org.uk>
Reported-by: syzbot+82defefbbd8527e1c2cb(a)syzkaller.appspotmail.com
Signed-off-by: Will Deacon <will(a)kernel.org>
Cc: stable <stable(a)vger.kernel.org>
Link: https://lore.kernel.org/r/20191219120203.32691-1-will@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org>
---
fs/char_dev.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/char_dev.c b/fs/char_dev.c
index 00dfe17871ac..c5e6eff5a381 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -352,7 +352,7 @@ static struct kobject *cdev_get(struct cdev *p)
if (owner && !try_module_get(owner))
return NULL;
- kobj = kobject_get(&p->kobj);
+ kobj = kobject_get_unless_zero(&p->kobj);
if (!kobj)
module_put(owner);
return kobj;
--
2.24.1
The rseq.h UAPI documents that the rseq_cs field must be cleared
before reclaiming memory that contains the targeted struct rseq_cs.
We should extend this comment to also dictate that the rseq_cs field
must be cleared before reclaiming memory of the code pointed to by
the rseq_cs start_ip and post_commit_offset fields.
While we can expect that use of dlclose(3) will typically unmap
both struct rseq_cs and its associated code at once, nothing would
theoretically prevent a JIT from reclaiming the code without
reclaiming the struct rseq_cs, which would erroneously allow the
kernel to consider new code which is not a rseq critical section
as a rseq critical section following a code reclaim.
Suggested-by: Florian Weimer <fw(a)deneb.enyo.de>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers(a)efficios.com>
Cc: Florian Weimer <fw(a)deneb.enyo.de>
Cc: Thomas Gleixner <tglx(a)linutronix.de>
Cc: Peter Zijlstra (Intel) <peterz(a)infradead.org>
Cc: "Paul E. McKenney" <paulmck(a)linux.ibm.com>
Cc: Boqun Feng <boqun.feng(a)gmail.com>
Cc: "H . Peter Anvin" <hpa(a)zytor.com>
Cc: Paul Turner <pjt(a)google.com>
Cc: Dmitry Vyukov <dvyukov(a)google.com>
Cc: Neel Natu <neelnatu(a)google.com>
Cc: linux-api(a)vger.kernel.org
---
include/uapi/linux/rseq.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h
index 9a402fdb60e9..d94afdfc4b7c 100644
--- a/include/uapi/linux/rseq.h
+++ b/include/uapi/linux/rseq.h
@@ -100,7 +100,9 @@ struct rseq {
* instruction sequence block, as well as when the kernel detects that
* it is preempting or delivering a signal outside of the range
* targeted by the rseq_cs. Also needs to be set to NULL by user-space
- * before reclaiming memory that contains the targeted struct rseq_cs.
+ * before reclaiming memory that contains the targeted struct rseq_cs
+ * or reclaiming memory that contains the code referred to by the
+ * start_ip and post_commit_offset fields of struct rseq_cs.
*
* Read and set by the kernel. Set by user-space with single-copy
* atomicity semantics. This field should only be updated by the
--
2.17.1
Be sure to initialise the uabi_instance on the virtual engine to the
special invalid value, just in case we ever peek at it from the uAPI.
Reported-by: Tvrtko Ursulin <tvrtko.ursulin(a)intel.com>
Fixes: 750e76b4f9f6 ("drm/i915/gt: Move the [class][inst] lookup for engines onto the GT")
Signed-off-by: Chris Wilson <chris(a)chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin(a)intel.com>
Cc: <stable(a)vger.kernel.org> # v5.4+
---
drivers/gpu/drm/i915/gt/intel_lrc.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 170b5a0139a3..f07d93514a7c 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -4601,9 +4601,11 @@ intel_execlists_create_virtual(struct intel_engine_cs **siblings,
ve->base.gt = siblings[0]->gt;
ve->base.uncore = siblings[0]->uncore;
ve->base.id = -1;
+
ve->base.class = OTHER_CLASS;
ve->base.uabi_class = I915_ENGINE_CLASS_INVALID;
ve->base.instance = I915_ENGINE_CLASS_INVALID_VIRTUAL;
+ ve->base.uabi_instance = I915_ENGINE_CLASS_INVALID_VIRTUAL;
/*
* The decision on whether to submit a request using semaphores
--
2.25.0.rc1