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>