Ives van Hoorne from codesandbox.io reported an issue regarding possible
data loss of uffd-wp when applied to memfds on heavily loaded systems. The
symptom is some read page got data mismatch from the snapshot child VMs.
Here I can also reproduce with a Rust reproducer that was provided by Ives
that keeps taking snapshot of a 256MB VM, on a 32G system when I initiate
80 instances I can trigger the issues in ten minutes.
It turns out that we got some pages write-through even if uffd-wp is
applied to the pte.
The problem is, when removing migration entries, we didn't really worry
about write bit as long as we know it's not a write migration entry. That
may not be true, for some memory types (e.g. writable shmem) mk_pte can
return a pte with write bit set, then to recover the migration entry to its
original state we need to explicit wr-protect the pte or it'll has the
write bit set if it's a read migration entry. For uffd it can cause
write-through.
The relevant code on uffd was introduced in the anon support, which is
commit f45ec5ff16a7 ("userfaultfd: wp: support swap and page migration",
2020-04-07). However anon shouldn't suffer from this problem because anon
should already have the write bit cleared always, so that may not be a
proper Fixes target, while I'm adding the Fixes to be uffd shmem support.
Cc: Andrea Arcangeli <aarcange(a)redhat.com>
Cc: stable(a)vger.kernel.org
Fixes: b1f9e876862d ("mm/uffd: enable write protection for shmem & hugetlbfs")
Reported-by: Ives van Hoorne <ives(a)codesandbox.io>
Reviewed-by: Alistair Popple <apopple(a)nvidia.com>
Tested-by: Ives van Hoorne <ives(a)codesandbox.io>
Signed-off-by: Peter Xu <peterx(a)redhat.com>
---
mm/migrate.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/mm/migrate.c b/mm/migrate.c
index dff333593a8a..8b6351c08c78 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -213,8 +213,14 @@ static bool remove_migration_pte(struct folio *folio,
pte = pte_mkdirty(pte);
if (is_writable_migration_entry(entry))
pte = maybe_mkwrite(pte, vma);
- else if (pte_swp_uffd_wp(*pvmw.pte))
+ else
+ /* NOTE: mk_pte can have write bit set */
+ pte = pte_wrprotect(pte);
+
+ if (pte_swp_uffd_wp(*pvmw.pte)) {
+ WARN_ON_ONCE(pte_write(pte));
pte = pte_mkuffd_wp(pte);
+ }
if (folio_test_anon(folio) && !is_readable_migration_entry(entry))
rmap_flags |= RMAP_EXCLUSIVE;
--
2.37.3
On Wed, Nov 30 2022 at 23:36, Sean Christopherson wrote:
> Fix a double NMI shootdown bug found and debugged by Guilherme, who did all
> the hard work. NMI shootdown is a one-time thing; the handler leaves NMIs
> blocked and enters halt. At best, a second (or third...) shootdown is an
> expensive nop, at worst it can hang the kernel and prevent kexec'ing into
> a new kernel, e.g. prior to the hardening of register_nmi_handler(), a
> double shootdown resulted in a double list_add(), which is fatal when running
> with CONFIG_BUG_ON_DATA_CORRUPTION=y.
>
> With the "right" kexec/kdump configuration, emergency_vmx_disable_all() can
> be reached after kdump_nmi_shootdown_cpus() (currently the only two users
> of nmi_shootdown_cpus()).
>
> To fix, move the disabling of virtualization into crash_nmi_callback(),
> remove emergency_vmx_disable_all()'s callback, and do a shootdown for
> emergency_vmx_disable_all() if and only if a shootdown hasn't yet occurred.
> The only thing emergency_vmx_disable_all() cares about is disabling VMX/SVM
> (obviously), and since I can't envision a use case for an NMI shootdown that
> doesn't want to disable virtualization, doing that in the core handler means
> emergency_vmx_disable_all() only needs to ensure _a_ shootdown occurs, it
> doesn't care when that shootdown happened or what callback may have run.
Reviewed-by: Thomas Gleixner <tglx(a)linutronix.de>
The LTP test pty03 is causing a crash in slcan:
BUG: kernel NULL pointer dereference, address: 0000000000000008
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP NOPTI
CPU: 0 PID: 348 Comm: kworker/0:3 Not tainted 6.0.8-1-default #1 openSUSE Tumbleweed 9d20364b934f5aab0a9bdf84e8f45cfdfae39dab
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.15.0-0-g2dd4b9b-rebuilt.opensuse.org 04/01/2014
Workqueue: 0x0 (events)
RIP: 0010:process_one_work (/home/rich/kernel/linux/kernel/workqueue.c:706 /home/rich/kernel/linux/kernel/workqueue.c:2185)
Code: 49 89 ff 41 56 41 55 41 54 55 53 48 89 f3 48 83 ec 10 48 8b 06 48 8b 6f 48 49 89 c4 45 30 e4 a8 04 b8 00 00 00 00 4c 0f 44 e0 <49> 8b 44 24 08 44 8b a8 00 01 00 00 41 83 e5 20 f6 45 10 04 75 0e
RSP: 0018:ffffaf7b40f47e98 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff9d644e1b8b48 RCX: ffff9d649e439968
RDX: 00000000ffff8455 RSI: ffff9d644e1b8b48 RDI: ffff9d64764aa6c0
RBP: ffff9d649e4335c0 R08: 0000000000000c00 R09: ffff9d64764aa734
R10: 0000000000000007 R11: 0000000000000001 R12: 0000000000000000
R13: ffff9d649e4335e8 R14: ffff9d64490da780 R15: ffff9d64764aa6c0
FS: 0000000000000000(0000) GS:ffff9d649e400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000008 CR3: 0000000036424000 CR4: 00000000000006f0
Call Trace:
<TASK>
worker_thread (/home/rich/kernel/linux/kernel/workqueue.c:2436)
kthread (/home/rich/kernel/linux/kernel/kthread.c:376)
ret_from_fork (/home/rich/kernel/linux/arch/x86/entry/entry_64.S:312)
Apparently, the slcan's tx_work is freed while being scheduled. While
slcan_netdev_close() (netdev side) calls flush_work(&sl->tx_work),
slcan_close() (tty side) does not. So when the netdev is never set UP,
but the tty is stuffed with bytes and forced to wakeup write, the work
is scheduled, but never flushed.
So add an additional flush_work() to slcan_close() to be sure the work
is flushed under all circumstances.
The Fixes commit below moved flush_work() from slcan_close() to
slcan_netdev_close(). What was the rationale behind it? Maybe we can
drop the one in slcan_netdev_close()?
I see the same pattern in can327. So it perhaps needs the very same fix.
Fixes: cfcb4465e992 ("can: slcan: remove legacy infrastructure")
Link: https://bugzilla.suse.com/show_bug.cgi?id=1205597
Reported-by: Richard Palethorpe <richard.palethorpe(a)suse.com>
Tested-by: Petr Vorel <petr.vorel(a)suse.com>
Cc: Dario Binacchi <dario.binacchi(a)amarulasolutions.com>
Cc: Wolfgang Grandegger <wg(a)grandegger.com>
Cc: Marc Kleine-Budde <mkl(a)pengutronix.de>
Cc: "David S. Miller" <davem(a)davemloft.net>
Cc: Eric Dumazet <edumazet(a)google.com>
Cc: Jakub Kicinski <kuba(a)kernel.org>
Cc: Paolo Abeni <pabeni(a)redhat.com>
Cc: linux-can(a)vger.kernel.org
Cc: netdev(a)vger.kernel.org
Cc: stable(a)vger.kernel.org
Cc: Max Staudt <max(a)enpas.org>
Signed-off-by: Jiri Slaby (SUSE) <jirislaby(a)kernel.org>
---
drivers/net/can/slcan/slcan-core.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/net/can/slcan/slcan-core.c b/drivers/net/can/slcan/slcan-core.c
index fbb34139daa1..f4db77007c13 100644
--- a/drivers/net/can/slcan/slcan-core.c
+++ b/drivers/net/can/slcan/slcan-core.c
@@ -864,12 +864,14 @@ static void slcan_close(struct tty_struct *tty)
{
struct slcan *sl = (struct slcan *)tty->disc_data;
- /* unregister_netdev() calls .ndo_stop() so we don't have to.
- * Our .ndo_stop() also flushes the TTY write wakeup handler,
- * so we can safely set sl->tty = NULL after this.
- */
unregister_candev(sl->dev);
+ /*
+ * The netdev needn't be UP (so .ndo_stop() is not called). Hence make
+ * sure this is not running before freeing it up.
+ */
+ flush_work(&sl->tx_work);
+
/* Mark channel as dead */
spin_lock_bh(&sl->lock);
tty->disc_data = NULL;
--
2.38.1
--
تم إرسال بريد إليك في وقت ما الأسبوع الماضي مع توقع
تلقي بريد عودة منك ولكن لدهشتي لم تكلف نفسك عناء الرد.
يرجى الرد لمزيد من الإيضاحات.
مع الاحترام لك،
كين جي ريتشاردسون.
This series fixes following issues:
Patch 1:
This patch provides a fix to correctly report encapsulated LRO'ed
packet.
Patch 2:
This patch provides a fix to use correct intrConf reference.
Changes in v2:
- declare generic descriptor to be used
- remove white spaces
- remove single quote around commit reference in patch 2
- remove if check for encap_lro
Ronak Doshi (2):
vmxnet3: correctly report encapsulated LRO packet
vmxnet3: use correct intrConf reference when using extended queues
drivers/net/vmxnet3/vmxnet3_drv.c | 27 +++++++++++++++++++++++----
1 file changed, 23 insertions(+), 4 deletions(-)
--
2.11.0