The patch titled
Subject: proc: fix PIE proc-empty-vm, proc-pid-vm tests
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
proc-fix-pie-proc-empty-vm-proc-pid-vm-tests.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patche…
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Alexey Dobriyan <adobriyan(a)gmail.com>
Subject: proc: fix PIE proc-empty-vm, proc-pid-vm tests
Date: Fri, 6 Jan 2023 22:30:14 +0300
vsyscall detection code uses direct call to the beginning of
the vsyscall page:
asm ("call %P0" :: "i" (0xffffffffff600000))
It generates "call rel32" instruction but it is not relocated if binary
is PIE, so binary segfaults into random userspace address and vsyscall
page status is detected incorrectly.
Do more direct:
asm ("call *%rax")
which doesn't do need any relocaltions.
Mark g_vsyscall as volatile for a good measure, I didn't find instruction
setting it to 0. Now the code is obviously correct:
xor eax, eax
mov rdi, rbp
mov rsi, rbp
mov DWORD PTR [rip+0x2d15], eax # g_vsyscall = 0
mov rax, 0xffffffffff600000
call rax
mov DWORD PTR [rip+0x2d02], 1 # g_vsyscall = 1
mov eax, DWORD PTR ds:0xffffffffff600000
mov DWORD PTR [rip+0x2cf1], 2 # g_vsyscall = 2
mov edi, [rip+0x2ceb] # exit(g_vsyscall)
call exit
Note: fixed proc-empty-vm test oopses 5.19.0-28-generic kernel
but this is separate story.
Link: https://lkml.kernel.org/r/Y7h2xvzKLg36DSq8@p183
Fixes: 5bc73bb3451b9 ("proc: test how it holds up with mapping'less process")
Signed-off-by: Alexey Dobriyan <adobriyan(a)gmail.com>
Reported-by: Mirsad Goran Todorovac <mirsad.todorovac(a)alu.unizg.hr>
Tested-by: Mirsad Goran Todorovac <mirsad.todorovac(a)alu.unizg.hr>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
tools/testing/selftests/proc/proc-empty-vm.c | 12 +++++++-----
tools/testing/selftests/proc/proc-pid-vm.c | 9 +++++----
2 files changed, 12 insertions(+), 9 deletions(-)
--- a/tools/testing/selftests/proc/proc-empty-vm.c~proc-fix-pie-proc-empty-vm-proc-pid-vm-tests
+++ a/tools/testing/selftests/proc/proc-empty-vm.c
@@ -25,6 +25,7 @@
#undef NDEBUG
#include <assert.h>
#include <errno.h>
+#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
@@ -41,7 +42,7 @@
* 1: vsyscall VMA is --xp vsyscall=xonly
* 2: vsyscall VMA is r-xp vsyscall=emulate
*/
-static int g_vsyscall;
+static volatile int g_vsyscall;
static const char *g_proc_pid_maps_vsyscall;
static const char *g_proc_pid_smaps_vsyscall;
@@ -147,11 +148,12 @@ static void vsyscall(void)
g_vsyscall = 0;
/* gettimeofday(NULL, NULL); */
+ uint64_t rax = 0xffffffffff600000;
asm volatile (
- "call %P0"
- :
- : "i" (0xffffffffff600000), "D" (NULL), "S" (NULL)
- : "rax", "rcx", "r11"
+ "call *%[rax]"
+ : [rax] "+a" (rax)
+ : "D" (NULL), "S" (NULL)
+ : "rcx", "r11"
);
g_vsyscall = 1;
--- a/tools/testing/selftests/proc/proc-pid-vm.c~proc-fix-pie-proc-empty-vm-proc-pid-vm-tests
+++ a/tools/testing/selftests/proc/proc-pid-vm.c
@@ -257,11 +257,12 @@ static void vsyscall(void)
g_vsyscall = 0;
/* gettimeofday(NULL, NULL); */
+ uint64_t rax = 0xffffffffff600000;
asm volatile (
- "call %P0"
- :
- : "i" (0xffffffffff600000), "D" (NULL), "S" (NULL)
- : "rax", "rcx", "r11"
+ "call *%[rax]"
+ : [rax] "+a" (rax)
+ : "D" (NULL), "S" (NULL)
+ : "rcx", "r11"
);
g_vsyscall = 1;
_
Patches currently in -mm which might be from adobriyan(a)gmail.com are
proc-fix-pie-proc-empty-vm-proc-pid-vm-tests.patch
proc-mark-proc-cmdline-as-permanent.patch
usb_kill_urb warranties that all the handlers are finished when it
returns, but does not protect against threads that might be handling
asynchronously the urb.
For UVC, the function uvc_ctrl_status_event_async() takes care of
control changes asynchronously.
If the code is executed in the following order:
CPU 0 CPU 1
===== =====
uvc_status_complete()
uvc_status_stop()
uvc_ctrl_status_event_work()
uvc_status_start() -> FAIL
Then uvc_status_start will keep failing and this error will be shown:
<4>[ 5.540139] URB 0000000000000000 submitted while active
drivers/usb/core/urb.c:378 usb_submit_urb+0x4c3/0x528
Let's improve the current situation, by not re-submiting the urb if
we are stopping the status event. Also process the queued work
(if any) during stop.
CPU 0 CPU 1
===== =====
uvc_status_complete()
uvc_status_stop()
uvc_status_start()
uvc_ctrl_status_event_work() -> FAIL
Hopefully, with the usb layer protection this should be enough to cover
all the cases.
Cc: stable(a)vger.kernel.org
Fixes: e5225c820c05 ("media: uvcvideo: Send a control event when a Control Change interrupt arrives")
Reviewed-by: Yunke Cao <yunkec(a)chromium.org>
Signed-off-by: Ricardo Ribalda <ribalda(a)chromium.org>
---
uvc: Fix race condition on uvc
Make sure that all the async work is finished when we stop the status urb.
To: Hillf Danton <hdanton(a)sina.com>
To: Yunke Cao <yunkec(a)chromium.org>
To: Sergey Senozhatsky <senozhatsky(a)chromium.org>
To: Max Staudt <mstaudt(a)google.com>
To: Laurent Pinchart <laurent.pinchart(a)ideasonboard.com>
To: Mauro Carvalho Chehab <mchehab(a)kernel.org>
Cc: linux-media(a)vger.kernel.org
Cc: linux-kernel(a)vger.kernel.org
---
Changes in v7:
- Use smp_store_release. (Thanks Hilf!)
- Rebase on top of uvc/next.
- Link to v6: https://lore.kernel.org/r/20221212-uvc-race-v6-0-2a662f8de011@chromium.org
Changes in v6:
- Improve comments. (Thanks Laurent).
- Use true/false instead of 1/0 (Thanks Laurent).
- Link to v5: https://lore.kernel.org/r/20221212-uvc-race-v5-0-3db3933d1608@chromium.org
Changes in v5:
- atomic_t do not impose barriers, use smp_mb() instead. (Thanks Laurent)
- Add an extra cancel_work_sync().
- Link to v4: https://lore.kernel.org/r/20221212-uvc-race-v4-0-38d7075b03f5@chromium.org
Changes in v4:
- Replace bool with atomic_t to avoid compiler reordering.
- First complete the async work and then kill the urb to avoid race (Thanks Laurent!)
- Link to v3: https://lore.kernel.org/r/20221212-uvc-race-v3-0-954efc752c9a@chromium.org
Changes in v3:
- Remove the patch for dev->status, makes more sense in another series, and makes
the zero day less nervous.
- Update reviewed-by (thanks Yunke!).
- Link to v2: https://lore.kernel.org/r/20221212-uvc-race-v2-0-54496cc3b8ab@chromium.org
Changes in v2:
- Add a patch for not kalloc dev->status
- Redo the logic mechanism, so it also works with suspend (Thanks Yunke!)
- Link to v1: https://lore.kernel.org/r/20221212-uvc-race-v1-0-c52e1783c31d@chromium.org
---
drivers/media/usb/uvc/uvc_ctrl.c | 5 +++++
drivers/media/usb/uvc/uvc_status.c | 33 +++++++++++++++++++++++++++++++++
drivers/media/usb/uvc/uvcvideo.h | 1 +
3 files changed, 39 insertions(+)
diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index e07b56bbf853..30c417768376 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -6,6 +6,7 @@
* Laurent Pinchart (laurent.pinchart(a)ideasonboard.com)
*/
+#include <asm/barrier.h>
#include <linux/bitops.h>
#include <linux/kernel.h>
#include <linux/list.h>
@@ -1509,6 +1510,10 @@ static void uvc_ctrl_status_event_work(struct work_struct *work)
uvc_ctrl_status_event(w->chain, w->ctrl, w->data);
+ /* The barrier is needed to synchronize with uvc_status_stop(). */
+ if (smp_load_acquire(&dev->flush_status))
+ return;
+
/* Resubmit the URB. */
w->urb->interval = dev->int_ep->desc.bInterval;
ret = usb_submit_urb(w->urb, GFP_KERNEL);
diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c
index 602830a8023e..21e13b8441da 100644
--- a/drivers/media/usb/uvc/uvc_status.c
+++ b/drivers/media/usb/uvc/uvc_status.c
@@ -6,6 +6,7 @@
* Laurent Pinchart (laurent.pinchart(a)ideasonboard.com)
*/
+#include <asm/barrier.h>
#include <linux/kernel.h>
#include <linux/input.h>
#include <linux/slab.h>
@@ -311,5 +312,37 @@ int uvc_status_start(struct uvc_device *dev, gfp_t flags)
void uvc_status_stop(struct uvc_device *dev)
{
+ struct uvc_ctrl_work *w = &dev->async_ctrl;
+
+ /*
+ * Prevent the asynchronous control handler from requeing the URB. The
+ * barrier is needed so the flush_status change is visible to other
+ * CPUs running the asynchronous handler before usb_kill_urb() is
+ * called below.
+ */
+ smp_store_release(&dev->flush_status, true);
+
+ /* If there is any status event on the queue, process it. */
+ if (cancel_work_sync(&w->work))
+ uvc_ctrl_status_event(w->chain, w->ctrl, w->data);
+
+ /* Kill the urb. */
usb_kill_urb(dev->int_urb);
+
+ /*
+ * The URB completion handler may have queued asynchronous work. This
+ * won't resubmit the URB as flush_status is set, but it needs to be
+ * cancelled before returning or it could then race with a future
+ * uvc_status_start() call.
+ */
+ if (cancel_work_sync(&w->work))
+ uvc_ctrl_status_event(w->chain, w->ctrl, w->data);
+
+ /*
+ * From this point, there are no events on the queue and the status URB
+ * is dead, this is, no events will be queued until uvc_status_start()
+ * is called. The barrier is needed to make sure that it is written to
+ * memory before uvc_status_start() is called again.
+ */
+ smp_store_release(&dev->flush_status, false);
}
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index ae0066eceffd..b2b277cccbdb 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -578,6 +578,7 @@ struct uvc_device {
struct usb_host_endpoint *int_ep;
struct urb *int_urb;
struct uvc_status *status;
+ bool flush_status;
struct input_dev *input;
char input_phys[64];
---
base-commit: fb1316b0ff3fc3cd98637040ee17ab7be753aac7
change-id: 20221212-uvc-race-09276ea68bf8
Best regards,
--
Ricardo Ribalda <ribalda(a)chromium.org>
On Fri, Jan 6, 2023 at 6:04 PM Luigi Semenzato <semenzato(a)chromium.org> wrote:
>
> I worked a fair amount on TPM 1.0 about 10 years ago and I even vaguely remember suspend-related problems. I'd be happy to take a look. The linked thread shows that Peter Huewe was copied. I know Peter well, his opinion can be trusted. Unfortunately I don't immediately see a link to a patch, can you help?
Sorry, I should have included that:
https://lore.kernel.org/lkml/20230106030156.3258307-1-Jason@zx2c4.com/
Instead of blocking system suspend when TPM_ORD_SAVESTATE fails, it
just lets the system sleep anyway. This means that presumably the
system might sleep without having called TPM_ORD_SAVESTATE. Trying to
figure out how bad that is.
And yes, Peter Huewe certainly knows about TPMs, especially as he
maintains the code in Linux, but the maintainers haven't been so much
available, unfortunately. This bug happens to intersect with something
mostly related that I work on (the rng), so I'm motivated to at least
prevent the worst of the breakage, but I otherwise don't know anything
about the Linux TPM driver.
Jason