pstore_dump() is *always* invoked in atomic context (nowadays in an RCU
read-side critical section, before that under a spinlock).
It doesn't make sense to try to use semaphores here.
This is mostly a revert of commit ea84b580b955 ("pstore: Convert buf_lock
to semaphore"), except that two parts aren't restored back exactly as they
were:
- keep the lock initialization in pstore_register
- in efi_pstore_write(), always set the "block" flag to false
- omit "is_locked", that was unnecessary since
commit 959217c84c27 ("pstore: Actually give up during locking failure")
- fix the bailout message
The actual problem that the buggy commit was trying to address may have
been that the use of preemptible() in efi_pstore_write() was wrong - it
only looks at preempt_count() and the state of IRQs, but __rcu_read_lock()
doesn't touch either of those under CONFIG_PREEMPT_RCU.
(Sidenote: CONFIG_PREEMPT_RCU means that the scheduler can preempt tasks in
RCU read-side critical sections, but you're not allowed to actively
block/reschedule.)
Lockdep probably never caught the problem because it's very rare that you
actually hit the contended case, so lockdep always just sees the
down_trylock(), not the down_interruptible(), and so it can't tell that
there's a problem.
Fixes: ea84b580b955 ("pstore: Convert buf_lock to semaphore")
Cc: stable(a)vger.kernel.org
Acked-by: Sebastian Andrzej Siewior <bigeasy(a)linutronix.de>
Signed-off-by: Jann Horn <jannh(a)google.com>
---
drivers/firmware/efi/efi-pstore.c | 2 +-
fs/pstore/platform.c | 38 +++++++++++++++----------------
include/linux/pstore.h | 6 ++---
3 files changed, 22 insertions(+), 24 deletions(-)
diff --git a/drivers/firmware/efi/efi-pstore.c b/drivers/firmware/efi/efi-pstore.c
index 0ef086e43090..7e771c56c13c 100644
--- a/drivers/firmware/efi/efi-pstore.c
+++ b/drivers/firmware/efi/efi-pstore.c
@@ -266,7 +266,7 @@ static int efi_pstore_write(struct pstore_record *record)
efi_name[i] = name[i];
ret = efivar_entry_set_safe(efi_name, vendor, PSTORE_EFI_ATTRIBUTES,
- preemptible(), record->size, record->psi->buf);
+ false, record->size, record->psi->buf);
if (record->reason == KMSG_DUMP_OOPS && try_module_get(THIS_MODULE))
if (!schedule_work(&efivar_work))
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index f243cb5e6a4f..e26162f102ff 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -143,21 +143,22 @@ static void pstore_timer_kick(void)
mod_timer(&pstore_timer, jiffies + msecs_to_jiffies(pstore_update_ms));
}
-/*
- * Should pstore_dump() wait for a concurrent pstore_dump()? If
- * not, the current pstore_dump() will report a failure to dump
- * and return.
- */
-static bool pstore_cannot_wait(enum kmsg_dump_reason reason)
+static bool pstore_cannot_block_path(enum kmsg_dump_reason reason)
{
- /* In NMI path, pstore shouldn't block regardless of reason. */
+ /*
+ * In case of NMI path, pstore shouldn't be blocked
+ * regardless of reason.
+ */
if (in_nmi())
return true;
switch (reason) {
/* In panic case, other cpus are stopped by smp_send_stop(). */
case KMSG_DUMP_PANIC:
- /* Emergency restart shouldn't be blocked. */
+ /*
+ * Emergency restart shouldn't be blocked by spinning on
+ * pstore_info::buf_lock.
+ */
case KMSG_DUMP_EMERG:
return true;
default:
@@ -389,21 +390,19 @@ static void pstore_dump(struct kmsg_dumper *dumper,
unsigned long total = 0;
const char *why;
unsigned int part = 1;
+ unsigned long flags = 0;
int ret;
why = kmsg_dump_reason_str(reason);
- if (down_trylock(&psinfo->buf_lock)) {
- /* Failed to acquire lock: give up if we cannot wait. */
- if (pstore_cannot_wait(reason)) {
- pr_err("dump skipped in %s path: may corrupt error record\n",
- in_nmi() ? "NMI" : why);
- return;
- }
- if (down_interruptible(&psinfo->buf_lock)) {
- pr_err("could not grab semaphore?!\n");
+ if (pstore_cannot_block_path(reason)) {
+ if (!spin_trylock_irqsave(&psinfo->buf_lock, flags)) {
+ pr_err("dump skipped in %s path because of concurrent dump\n",
+ in_nmi() ? "NMI" : why);
return;
}
+ } else {
+ spin_lock_irqsave(&psinfo->buf_lock, flags);
}
kmsg_dump_rewind(&iter);
@@ -467,8 +466,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
total += record.size;
part++;
}
-
- up(&psinfo->buf_lock);
+ spin_unlock_irqrestore(&psinfo->buf_lock, flags);
}
static struct kmsg_dumper pstore_dumper = {
@@ -594,7 +592,7 @@ int pstore_register(struct pstore_info *psi)
psi->write_user = pstore_write_user_compat;
psinfo = psi;
mutex_init(&psinfo->read_mutex);
- sema_init(&psinfo->buf_lock, 1);
+ spin_lock_init(&psinfo->buf_lock);
if (psi->flags & PSTORE_FLAGS_DMESG)
allocate_buf_for_compression();
diff --git a/include/linux/pstore.h b/include/linux/pstore.h
index eb93a54cff31..e97a8188f0fd 100644
--- a/include/linux/pstore.h
+++ b/include/linux/pstore.h
@@ -14,7 +14,7 @@
#include <linux/errno.h>
#include <linux/kmsg_dump.h>
#include <linux/mutex.h>
-#include <linux/semaphore.h>
+#include <linux/spinlock.h>
#include <linux/time.h>
#include <linux/types.h>
@@ -87,7 +87,7 @@ struct pstore_record {
* @owner: module which is responsible for this backend driver
* @name: name of the backend driver
*
- * @buf_lock: semaphore to serialize access to @buf
+ * @buf_lock: spinlock to serialize access to @buf
* @buf: preallocated crash dump buffer
* @bufsize: size of @buf available for crash dump bytes (must match
* smallest number of bytes available for writing to a
@@ -178,7 +178,7 @@ struct pstore_info {
struct module *owner;
const char *name;
- struct semaphore buf_lock;
+ spinlock_t buf_lock;
char *buf;
size_t bufsize;
base-commit: 83e396641110663d3c7bb25b9bc0c6a750359ecf
--
2.35.1.723.g4982287a31-goog
This is a note to let you know that I've just added the patch titled
usb: gadget: Fix use-after-free bug by not setting udc->dev.driver
to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus 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 hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
From 16b1941eac2bd499f065a6739a40ce0011a3d740 Mon Sep 17 00:00:00 2001
From: Alan Stern <stern(a)rowland.harvard.edu>
Date: Sat, 5 Mar 2022 21:47:22 -0500
Subject: usb: gadget: Fix use-after-free bug by not setting udc->dev.driver
The syzbot fuzzer found a use-after-free bug:
BUG: KASAN: use-after-free in dev_uevent+0x712/0x780 drivers/base/core.c:2320
Read of size 8 at addr ffff88802b934098 by task udevd/3689
CPU: 2 PID: 3689 Comm: udevd Not tainted 5.17.0-rc4-syzkaller-00229-g4f12b742eb2b #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_address_description.constprop.0.cold+0x8d/0x303 mm/kasan/report.c:255
__kasan_report mm/kasan/report.c:442 [inline]
kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
dev_uevent+0x712/0x780 drivers/base/core.c:2320
uevent_show+0x1b8/0x380 drivers/base/core.c:2391
dev_attr_show+0x4b/0x90 drivers/base/core.c:2094
Although the bug manifested in the driver core, the real cause was a
race with the gadget core. dev_uevent() does:
if (dev->driver)
add_uevent_var(env, "DRIVER=%s", dev->driver->name);
and between the test and the dereference of dev->driver, the gadget
core sets dev->driver to NULL.
The race wouldn't occur if the gadget core registered its devices on
a real bus, using the standard synchronization techniques of the
driver core. However, it's not necessary to make such a large change
in order to fix this bug; all we need to do is make sure that
udc->dev.driver is always NULL.
In fact, there is no reason for udc->dev.driver ever to be set to
anything, let alone to the value it currently gets: the address of the
gadget's driver. After all, a gadget driver only knows how to manage
a gadget, not how to manage a UDC.
This patch simply removes the statements in the gadget core that touch
udc->dev.driver.
Fixes: 2ccea03a8f7e ("usb: gadget: introduce UDC Class")
CC: <stable(a)vger.kernel.org>
Reported-and-tested-by: syzbot+348b571beb5eeb70a582(a)syzkaller.appspotmail.com
Signed-off-by: Alan Stern <stern(a)rowland.harvard.edu>
Link: https://lore.kernel.org/r/YiQgukfFFbBnwJ/9@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org>
---
drivers/usb/gadget/udc/core.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index 568534a0d17c..c109b069f511 100644
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -1436,7 +1436,6 @@ static void usb_gadget_remove_driver(struct usb_udc *udc)
usb_gadget_udc_stop(udc);
udc->driver = NULL;
- udc->dev.driver = NULL;
udc->gadget->dev.driver = NULL;
}
@@ -1498,7 +1497,6 @@ static int udc_bind_to_driver(struct usb_udc *udc, struct usb_gadget_driver *dri
driver->function);
udc->driver = driver;
- udc->dev.driver = &driver->driver;
udc->gadget->dev.driver = &driver->driver;
usb_gadget_udc_set_speed(udc, driver->max_speed);
@@ -1521,7 +1519,6 @@ static int udc_bind_to_driver(struct usb_udc *udc, struct usb_gadget_driver *dri
dev_err(&udc->dev, "failed to start %s: %d\n",
udc->driver->function, ret);
udc->driver = NULL;
- udc->dev.driver = NULL;
udc->gadget->dev.driver = NULL;
return ret;
}
--
2.35.1
This is a note to let you know that I've just added the patch titled
usb: usbtmc: Fix bug in pipe direction for control transfers
to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus 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 hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
From e9b667a82cdcfe21d590344447d65daed52b353b Mon Sep 17 00:00:00 2001
From: Alan Stern <stern(a)rowland.harvard.edu>
Date: Thu, 3 Mar 2022 16:00:17 -0500
Subject: usb: usbtmc: Fix bug in pipe direction for control transfers
The syzbot fuzzer reported a minor bug in the usbtmc driver:
usb 5-1: BOGUS control dir, pipe 80001e80 doesn't match bRequestType 0
WARNING: CPU: 0 PID: 3813 at drivers/usb/core/urb.c:412
usb_submit_urb+0x13a5/0x1970 drivers/usb/core/urb.c:410
Modules linked in:
CPU: 0 PID: 3813 Comm: syz-executor122 Not tainted
5.17.0-rc5-syzkaller-00306-g2293be58d6a1 #0
...
Call Trace:
<TASK>
usb_start_wait_urb+0x113/0x530 drivers/usb/core/message.c:58
usb_internal_control_msg drivers/usb/core/message.c:102 [inline]
usb_control_msg+0x2a5/0x4b0 drivers/usb/core/message.c:153
usbtmc_ioctl_request drivers/usb/class/usbtmc.c:1947 [inline]
The problem is that usbtmc_ioctl_request() uses usb_rcvctrlpipe() for
all of its transfers, whether they are in or out. It's easy to fix.
CC: <stable(a)vger.kernel.org>
Reported-and-tested-by: syzbot+a48e3d1a875240cab5de(a)syzkaller.appspotmail.com
Signed-off-by: Alan Stern <stern(a)rowland.harvard.edu>
Link: https://lore.kernel.org/r/YiEsYTPEE6lOCOA5@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org>
---
drivers/usb/class/usbtmc.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index 73f419adce61..4bb6d304eb4b 100644
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -1919,6 +1919,7 @@ static int usbtmc_ioctl_request(struct usbtmc_device_data *data,
struct usbtmc_ctrlrequest request;
u8 *buffer = NULL;
int rv;
+ unsigned int is_in, pipe;
unsigned long res;
res = copy_from_user(&request, arg, sizeof(struct usbtmc_ctrlrequest));
@@ -1928,12 +1929,14 @@ static int usbtmc_ioctl_request(struct usbtmc_device_data *data,
if (request.req.wLength > USBTMC_BUFSIZE)
return -EMSGSIZE;
+ is_in = request.req.bRequestType & USB_DIR_IN;
+
if (request.req.wLength) {
buffer = kmalloc(request.req.wLength, GFP_KERNEL);
if (!buffer)
return -ENOMEM;
- if ((request.req.bRequestType & USB_DIR_IN) == 0) {
+ if (!is_in) {
/* Send control data to device */
res = copy_from_user(buffer, request.data,
request.req.wLength);
@@ -1944,8 +1947,12 @@ static int usbtmc_ioctl_request(struct usbtmc_device_data *data,
}
}
+ if (is_in)
+ pipe = usb_rcvctrlpipe(data->usb_dev, 0);
+ else
+ pipe = usb_sndctrlpipe(data->usb_dev, 0);
rv = usb_control_msg(data->usb_dev,
- usb_rcvctrlpipe(data->usb_dev, 0),
+ pipe,
request.req.bRequest,
request.req.bRequestType,
request.req.wValue,
@@ -1957,7 +1964,7 @@ static int usbtmc_ioctl_request(struct usbtmc_device_data *data,
goto exit;
}
- if (rv && (request.req.bRequestType & USB_DIR_IN)) {
+ if (rv && is_in) {
/* Read control data from device */
res = copy_to_user(request.data, buffer, rv);
if (res)
--
2.35.1