A number of userspace utilities depend on making calls to RTAS to retrieve
information and update various things.
The existing API through which we expose RTAS to userspace exposes more
RTAS functionality than we actually need, through the sys_rtas syscall,
which allows root (or anyone with CAP_SYS_ADMIN) to make any RTAS call they
want with arbitrary arguments.
Many RTAS calls take the address of a buffer as an argument, and it's up to
the caller to specify the physical address of the buffer as an argument. We
allocate a buffer (the "RMO buffer") in the Real Memory Area that RTAS can
access, and then expose the physical address and size of this buffer in
/proc/powerpc/rtas/rmo_buffer. Userspace is expected to read this address,
poke at the buffer using /dev/mem, and pass an address in the RMO buffer to
the RTAS call.
However, there's nothing stopping the caller from specifying whatever
address they want in the RTAS call, and it's easy to construct a series of
RTAS calls that can overwrite arbitrary bytes (even without /dev/mem
access).
Additionally, there are some RTAS calls that do potentially dangerous
things and for which there are no legitimate userspace use cases.
In the past, this would not have been a particularly big deal as it was
assumed that root could modify all system state freely, but with Secure
Boot and lockdown we need to care about this.
We can't fundamentally change the ABI at this point, however we can address
this by implementing a filter that checks RTAS calls against a list
of permitted calls and forces the caller to use addresses within the RMO
buffer.
The list is based off the list of calls that are used by the librtas
userspace library, and has been tested with a number of existing userspace
RTAS utilities. For compatibility with any applications we are not aware of
that require other calls, the filter can be turned off at build time.
Reported-by: Daniel Axtens <dja(a)axtens.net>
Cc: stable(a)vger.kernel.org
Signed-off-by: Andrew Donnellan <ajd(a)linux.ibm.com>
---
v1->v2:
- address comments from mpe
- shorten the names of some struct members
- make the filter array static/ro_after_init, use const char *
- genericise the fixed buffer size cases
- simplify/get rid of some of the error printing
- get rid of rtas_token_name()
---
arch/powerpc/Kconfig | 13 ++++
arch/powerpc/kernel/rtas.c | 153 +++++++++++++++++++++++++++++++++++++
2 files changed, 166 insertions(+)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 1f48bbfb3ce9..8dd42b82379b 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -989,6 +989,19 @@ config PPC_SECVAR_SYSFS
read/write operations on these variables. Say Y if you have
secure boot enabled and want to expose variables to userspace.
+config PPC_RTAS_FILTER
+ bool "Enable filtering of RTAS syscalls"
+ default y
+ depends on PPC_RTAS
+ help
+ The RTAS syscall API has security issues that could be used to
+ compromise system integrity. This option enforces restrictions on the
+ RTAS calls and arguments passed by userspace programs to mitigate
+ these issues.
+
+ Say Y unless you know what you are doing and the filter is causing
+ problems for you.
+
endmenu
config ISA_DMA_API
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 806d554ce357..954f41676f69 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -992,6 +992,147 @@ struct pseries_errorlog *get_pseries_errorlog(struct rtas_error_log *log,
return NULL;
}
+#ifdef CONFIG_PPC_RTAS_FILTER
+
+/*
+ * The sys_rtas syscall, as originally designed, allows root to pass
+ * arbitrary physical addresses to RTAS calls. A number of RTAS calls
+ * can be abused to write to arbitrary memory and do other things that
+ * are potentially harmful to system integrity, and thus should only
+ * be used inside the kernel and not exposed to userspace.
+ *
+ * All known legitimate users of the sys_rtas syscall will only ever
+ * pass addresses that fall within the RMO buffer, and use a known
+ * subset of RTAS calls.
+ *
+ * Accordingly, we filter RTAS requests to check that the call is
+ * permitted, and that provided pointers fall within the RMO buffer.
+ * The rtas_filters list contains an entry for each permitted call,
+ * with the indexes of the parameters which are expected to contain
+ * addresses and sizes of buffers allocated inside the RMO buffer.
+ */
+struct rtas_filter {
+ const char *name;
+ int token;
+ /* Indexes into the args buffer, -1 if not used */
+ int buf_idx1;
+ int size_idx1;
+ int buf_idx2;
+ int size_idx2;
+
+ int fixed_size;
+};
+
+static struct rtas_filter rtas_filters[] __ro_after_init = {
+ { "ibm,activate-firmware", -1, -1, -1, -1, -1 },
+ { "ibm,configure-connector", -1, 0, -1, 1, -1, 4096 }, /* Special cased */
+ { "display-character", -1, -1, -1, -1, -1 },
+ { "ibm,display-message", -1, 0, -1, -1, -1 },
+ { "ibm,errinjct", -1, 2, -1, -1, -1, 1024 },
+ { "ibm,close-errinjct", -1, -1, -1, -1, -1 },
+ { "ibm,open-errinct", -1, -1, -1, -1, -1 },
+ { "ibm,get-config-addr-info2", -1, -1, -1, -1, -1 },
+ { "ibm,get-dynamic-sensor-state", -1, 1, -1, -1, -1 },
+ { "ibm,get-indices", -1, 2, 3, -1, -1 },
+ { "get-power-level", -1, -1, -1, -1, -1 },
+ { "get-sensor-state", -1, -1, -1, -1, -1 },
+ { "ibm,get-system-parameter", -1, 1, 2, -1, -1 },
+ { "get-time-of-day", -1, -1, -1, -1, -1 },
+ { "ibm,get-vpd", -1, 0, -1, 1, 2 },
+ { "ibm,lpar-perftools", -1, 2, 3, -1, -1 },
+ { "ibm,platform-dump", -1, 4, 5, -1, -1 },
+ { "ibm,read-slot-reset-state", -1, -1, -1, -1, -1 },
+ { "ibm,scan-log-dump", -1, 0, 1, -1, -1 },
+ { "ibm,set-dynamic-indicator", -1, 2, -1, -1, -1 },
+ { "ibm,set-eeh-option", -1, -1, -1, -1, -1 },
+ { "set-indicator", -1, -1, -1, -1, -1 },
+ { "set-power-level", -1, -1, -1, -1, -1 },
+ { "set-time-for-power-on", -1, -1, -1, -1, -1 },
+ { "ibm,set-system-parameter", -1, 1, -1, -1, -1 },
+ { "set-time-of-day", -1, -1, -1, -1, -1 },
+ { "ibm,suspend-me", -1, -1, -1, -1, -1 },
+ { "ibm,update-nodes", -1, 0, -1, -1, -1, 4096 },
+ { "ibm,update-properties", -1, 0, -1, -1, -1, 4096 },
+ { "ibm,physical-attestation", -1, 0, 1, -1, -1 },
+};
+
+static bool in_rmo_buf(u32 base, u32 end)
+{
+ return base >= rtas_rmo_buf &&
+ base < (rtas_rmo_buf + RTAS_RMOBUF_MAX) &&
+ base <= end &&
+ end >= rtas_rmo_buf &&
+ end < (rtas_rmo_buf + RTAS_RMOBUF_MAX);
+}
+
+static bool block_rtas_call(int token, int nargs,
+ struct rtas_args *args)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(rtas_filters); i++) {
+ struct rtas_filter *f = &rtas_filters[i];
+ u32 base, size, end;
+
+ if (token != f->token)
+ continue;
+
+ if (f->buf_idx1 != -1) {
+ base = be32_to_cpu(args->args[f->buf_idx1]);
+ if (f->size_idx1 != -1)
+ size = be32_to_cpu(args->args[f->size_idx1]);
+ else if (f->fixed_size)
+ size = f->fixed_size;
+ else
+ size = 1;
+
+ end = base + size - 1;
+ if (!in_rmo_buf(base, end))
+ goto err;
+ }
+
+ if (f->buf_idx2 != -1) {
+ base = be32_to_cpu(args->args[f->buf_idx2]);
+ if (f->size_idx2 != -1)
+ size = be32_to_cpu(args->args[f->size_idx2]);
+ else if (f->fixed_size)
+ size = f->fixed_size;
+ else
+ size = 1;
+ end = base + size - 1;
+
+ /*
+ * Special case for ibm,configure-connector where the
+ * address can be 0
+ */
+ if (!strcmp(f->name, "ibm,configure-connector") &&
+ base == 0)
+ return false;
+
+ if (!in_rmo_buf(base, end))
+ goto err;
+ }
+
+ return false;
+ }
+
+err:
+ pr_err_ratelimited("sys_rtas: RTAS call blocked - exploit attempt?\n");
+ pr_err_ratelimited("sys_rtas: token=0x%x, nargs=%d (called by %s)\n",
+ token, nargs, current->comm);
+ return true;
+}
+
+#else
+
+static bool block_rtas_call(int token, int nargs,
+ struct rtas_args *args)
+{
+ return false;
+}
+
+#endif /* CONFIG_PPC_RTAS_FILTER */
+
/* We assume to be passed big endian arguments */
SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)
{
@@ -1029,6 +1170,9 @@ SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)
args.rets = &args.args[nargs];
memset(args.rets, 0, nret * sizeof(rtas_arg_t));
+ if (block_rtas_call(token, nargs, &args))
+ return -EINVAL;
+
/* Need to handle ibm,suspend_me call specially */
if (token == ibm_suspend_me_token) {
@@ -1090,6 +1234,9 @@ void __init rtas_initialize(void)
unsigned long rtas_region = RTAS_INSTANTIATE_MAX;
u32 base, size, entry;
int no_base, no_size, no_entry;
+#ifdef CONFIG_PPC_RTAS_FILTER
+ int i;
+#endif
/* Get RTAS dev node and fill up our "rtas" structure with infos
* about it.
@@ -1129,6 +1276,12 @@ void __init rtas_initialize(void)
#ifdef CONFIG_RTAS_ERROR_LOGGING
rtas_last_error_token = rtas_token("rtas-last-error");
#endif
+
+#ifdef CONFIG_PPC_RTAS_FILTER
+ for (i = 0; i < ARRAY_SIZE(rtas_filters); i++) {
+ rtas_filters[i].token = rtas_token(rtas_filters[i].name);
+ }
+#endif
}
int __init early_init_dt_scan_rtas(unsigned long node,
--
2.20.1
The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 156abe2961601d60a8c2a60c6dc8dd6ce7adcdaf Mon Sep 17 00:00:00 2001
From: Hans de Goede <hdegoede(a)redhat.com>
Date: Sat, 6 Jun 2020 11:31:50 +0200
Subject: [PATCH] pinctrl: baytrail: Fix pin being driven low for a while on
gpiod_get(..., GPIOD_OUT_HIGH)
The pins on the Bay Trail SoC have separate input-buffer and output-buffer
enable bits and a read of the level bit of the value register will always
return the value from the input-buffer.
The BIOS of a device may configure a pin in output-only mode, only enabling
the output buffer, and write 1 to the level bit to drive the pin high.
This 1 written to the level bit will be stored inside the data-latch of the
output buffer.
But a subsequent read of the value register will return 0 for the level bit
because the input-buffer is disabled. This causes a read-modify-write as
done by byt_gpio_set_direction() to write 0 to the level bit, driving the
pin low!
Before this commit byt_gpio_direction_output() relied on
pinctrl_gpio_direction_output() to set the direction, followed by a call
to byt_gpio_set() to apply the selected value. This causes the pin to
go low between the pinctrl_gpio_direction_output() and byt_gpio_set()
calls.
Change byt_gpio_direction_output() to directly make the register
modifications itself instead. Replacing the 2 subsequent writes to the
value register with a single write.
Note that the pinctrl code does not keep track internally of the direction,
so not going through pinctrl_gpio_direction_output() is not an issue.
This issue was noticed on a Trekstor SurfTab Twin 10.1. When the panel is
already on at boot (no external monitor connected), then the i915 driver
does a gpiod_get(..., GPIOD_OUT_HIGH) for the panel-enable GPIO. The
temporarily going low of that GPIO was causing the panel to reset itself
after which it would not show an image until it was turned off and back on
again (until a full modeset was done on it). This commit fixes this.
This commit also updates the byt_gpio_direction_input() to use direct
register accesses instead of going through pinctrl_gpio_direction_input(),
to keep it consistent with byt_gpio_direction_output().
Note for backporting, this commit depends on:
commit e2b74419e5cc ("pinctrl: baytrail: Replace WARN with dev_info_once
when setting direct-irq pin to output")
Cc: stable(a)vger.kernel.org
Fixes: 86e3ef812fe3 ("pinctrl: baytrail: Update gpio chip operations")
Signed-off-by: Hans de Goede <hdegoede(a)redhat.com>
Acked-by: Mika Westerberg <mika.westerberg(a)linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko(a)linux.intel.com>
diff --git a/drivers/pinctrl/intel/pinctrl-baytrail.c b/drivers/pinctrl/intel/pinctrl-baytrail.c
index e3ceb3dfeabe..a917a2df520e 100644
--- a/drivers/pinctrl/intel/pinctrl-baytrail.c
+++ b/drivers/pinctrl/intel/pinctrl-baytrail.c
@@ -800,6 +800,21 @@ static void byt_gpio_disable_free(struct pinctrl_dev *pctl_dev,
pm_runtime_put(vg->dev);
}
+static void byt_gpio_direct_irq_check(struct intel_pinctrl *vg,
+ unsigned int offset)
+{
+ void __iomem *conf_reg = byt_gpio_reg(vg, offset, BYT_CONF0_REG);
+
+ /*
+ * Before making any direction modifications, do a check if gpio is set
+ * for direct IRQ. On Bay Trail, setting GPIO to output does not make
+ * sense, so let's at least inform the caller before they shoot
+ * themselves in the foot.
+ */
+ if (readl(conf_reg) & BYT_DIRECT_IRQ_EN)
+ dev_info_once(vg->dev, "Potential Error: Setting GPIO with direct_irq_en to output");
+}
+
static int byt_gpio_set_direction(struct pinctrl_dev *pctl_dev,
struct pinctrl_gpio_range *range,
unsigned int offset,
@@ -807,7 +822,6 @@ static int byt_gpio_set_direction(struct pinctrl_dev *pctl_dev,
{
struct intel_pinctrl *vg = pinctrl_dev_get_drvdata(pctl_dev);
void __iomem *val_reg = byt_gpio_reg(vg, offset, BYT_VAL_REG);
- void __iomem *conf_reg = byt_gpio_reg(vg, offset, BYT_CONF0_REG);
unsigned long flags;
u32 value;
@@ -817,14 +831,8 @@ static int byt_gpio_set_direction(struct pinctrl_dev *pctl_dev,
value &= ~BYT_DIR_MASK;
if (input)
value |= BYT_OUTPUT_EN;
- else if (readl(conf_reg) & BYT_DIRECT_IRQ_EN)
- /*
- * Before making any direction modifications, do a check if gpio
- * is set for direct IRQ. On baytrail, setting GPIO to output
- * does not make sense, so let's at least inform the caller before
- * they shoot themselves in the foot.
- */
- dev_info_once(vg->dev, "Potential Error: Setting GPIO with direct_irq_en to output");
+ else
+ byt_gpio_direct_irq_check(vg, offset);
writel(value, val_reg);
@@ -1165,19 +1173,50 @@ static int byt_gpio_get_direction(struct gpio_chip *chip, unsigned int offset)
static int byt_gpio_direction_input(struct gpio_chip *chip, unsigned int offset)
{
- return pinctrl_gpio_direction_input(chip->base + offset);
+ struct intel_pinctrl *vg = gpiochip_get_data(chip);
+ void __iomem *val_reg = byt_gpio_reg(vg, offset, BYT_VAL_REG);
+ unsigned long flags;
+ u32 reg;
+
+ raw_spin_lock_irqsave(&byt_lock, flags);
+
+ reg = readl(val_reg);
+ reg &= ~BYT_DIR_MASK;
+ reg |= BYT_OUTPUT_EN;
+ writel(reg, val_reg);
+
+ raw_spin_unlock_irqrestore(&byt_lock, flags);
+ return 0;
}
+/*
+ * Note despite the temptation this MUST NOT be converted into a call to
+ * pinctrl_gpio_direction_output() + byt_gpio_set() that does not work this
+ * MUST be done as a single BYT_VAL_REG register write.
+ * See the commit message of the commit adding this comment for details.
+ */
static int byt_gpio_direction_output(struct gpio_chip *chip,
unsigned int offset, int value)
{
- int ret = pinctrl_gpio_direction_output(chip->base + offset);
+ struct intel_pinctrl *vg = gpiochip_get_data(chip);
+ void __iomem *val_reg = byt_gpio_reg(vg, offset, BYT_VAL_REG);
+ unsigned long flags;
+ u32 reg;
- if (ret)
- return ret;
+ raw_spin_lock_irqsave(&byt_lock, flags);
+
+ byt_gpio_direct_irq_check(vg, offset);
- byt_gpio_set(chip, offset, value);
+ reg = readl(val_reg);
+ reg &= ~BYT_DIR_MASK;
+ if (value)
+ reg |= BYT_LEVEL;
+ else
+ reg &= ~BYT_LEVEL;
+ writel(reg, val_reg);
+
+ raw_spin_unlock_irqrestore(&byt_lock, flags);
return 0;
}
The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 39f23ce07b9355d05a64ae303ce20d1c4b92b957 Mon Sep 17 00:00:00 2001
From: Vincent Guittot <vincent.guittot(a)linaro.org>
Date: Wed, 13 May 2020 15:55:28 +0200
Subject: [PATCH] sched/fair: Fix unthrottle_cfs_rq() for leaf_cfs_rq list
Although not exactly identical, unthrottle_cfs_rq() and enqueue_task_fair()
are quite close and follow the same sequence for enqueuing an entity in the
cfs hierarchy. Modify unthrottle_cfs_rq() to use the same pattern as
enqueue_task_fair(). This fixes a problem already faced with the latter and
add an optimization in the last for_each_sched_entity loop.
Fixes: fe61468b2cb (sched/fair: Fix enqueue_task_fair warning)
Reported-by Tao Zhou <zohooouoto(a)zoho.com.cn>
Signed-off-by: Vincent Guittot <vincent.guittot(a)linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org>
Reviewed-by: Phil Auld <pauld(a)redhat.com>
Reviewed-by: Ben Segall <bsegall(a)google.com>
Link: https://lkml.kernel.org/r/20200513135528.4742-1-vincent.guittot@linaro.org
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c6d57c334d51..538ba5d94e99 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4774,7 +4774,6 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
struct rq *rq = rq_of(cfs_rq);
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
struct sched_entity *se;
- int enqueue = 1;
long task_delta, idle_task_delta;
se = cfs_rq->tg->se[cpu_of(rq)];
@@ -4798,26 +4797,44 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
idle_task_delta = cfs_rq->idle_h_nr_running;
for_each_sched_entity(se) {
if (se->on_rq)
- enqueue = 0;
+ break;
+ cfs_rq = cfs_rq_of(se);
+ enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
+ cfs_rq->h_nr_running += task_delta;
+ cfs_rq->idle_h_nr_running += idle_task_delta;
+
+ /* end evaluation on encountering a throttled cfs_rq */
+ if (cfs_rq_throttled(cfs_rq))
+ goto unthrottle_throttle;
+ }
+
+ for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
- if (enqueue) {
- enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
- } else {
- update_load_avg(cfs_rq, se, 0);
- se_update_runnable(se);
- }
+
+ update_load_avg(cfs_rq, se, UPDATE_TG);
+ se_update_runnable(se);
cfs_rq->h_nr_running += task_delta;
cfs_rq->idle_h_nr_running += idle_task_delta;
+
+ /* end evaluation on encountering a throttled cfs_rq */
if (cfs_rq_throttled(cfs_rq))
- break;
+ goto unthrottle_throttle;
+
+ /*
+ * One parent has been throttled and cfs_rq removed from the
+ * list. Add it back to not break the leaf list.
+ */
+ if (throttled_hierarchy(cfs_rq))
+ list_add_leaf_cfs_rq(cfs_rq);
}
- if (!se)
- add_nr_running(rq, task_delta);
+ /* At this point se is NULL and we are at root level*/
+ add_nr_running(rq, task_delta);
+unthrottle_throttle:
/*
* The cfs_rq_throttled() breaks in the above iteration can result in
* incomplete leaf list maintenance, resulting in triggering the
@@ -4826,7 +4843,8 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
- list_add_leaf_cfs_rq(cfs_rq);
+ if (list_add_leaf_cfs_rq(cfs_rq))
+ break;
}
assert_list_leaf_cfs_rq(rq);
In commit d8bb6718c4db ("arm64: Make debug exception handlers visible
from RCU") debug_exception_enter and exit were added to deal with better
tracking of RCU state - however, in addition to that, but not mentioned
in the commit log, a preempt_disable/enable pair were also added.
Based on the comment (being removed here) it would seem that the pair
were not added to address a specific problem, but just as a proactive,
preventative measure - as in "seemed like a good idea at the time".
The problem is that do_debug_exception() eventually calls out to
generic kernel code like do_force_sig_info() which takes non-raw locks
and on -rt enabled kernels, results in things looking like the following,
since on -rt kernels, it is noticed that preemption is still disabled.
BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:975
in_atomic(): 1, irqs_disabled(): 0, pid: 35658, name: gdbtest
Preemption disabled at:
[<ffff000010081578>] do_debug_exception+0x38/0x1a4
Call trace:
dump_backtrace+0x0/0x138
show_stack+0x24/0x30
dump_stack+0x94/0xbc
___might_sleep+0x13c/0x168
rt_spin_lock+0x40/0x80
do_force_sig_info+0x30/0xe0
force_sig_fault+0x64/0x90
arm64_force_sig_fault+0x50/0x80
send_user_sigtrap+0x50/0x80
brk_handler+0x98/0xc8
do_debug_exception+0x70/0x1a4
el0_dbg+0x18/0x20
The reproducer was basically an automated gdb test that set a breakpoint
on a simple "hello world" program and then quit gdb once the breakpoint
was hit - i.e. "(gdb) A debugging session is active. Quit anyway? "
Fixes: d8bb6718c4db ("arm64: Make debug exception handlers visible from RCU")
Cc: stable(a)vger.kernel.org
Cc: Naresh Kamboju <naresh.kamboju(a)linaro.org>
Cc: Paul E. McKenney <paulmck(a)linux.ibm.com>
Cc: Masami Hiramatsu <mhiramat(a)kernel.org>
Cc: Will Deacon <will(a)kernel.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker(a)windriver.com>
---
arch/arm64/mm/fault.c | 11 -----------
1 file changed, 11 deletions(-)
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 8afb238ff335..4d83ec991b33 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -788,13 +788,6 @@ void __init hook_debug_fault_code(int nr,
debug_fault_info[nr].name = name;
}
-/*
- * In debug exception context, we explicitly disable preemption despite
- * having interrupts disabled.
- * This serves two purposes: it makes it much less likely that we would
- * accidentally schedule in exception context and it will force a warning
- * if we somehow manage to schedule by accident.
- */
static void debug_exception_enter(struct pt_regs *regs)
{
/*
@@ -816,8 +809,6 @@ static void debug_exception_enter(struct pt_regs *regs)
rcu_nmi_enter();
}
- preempt_disable();
-
/* This code is a bit fragile. Test it. */
RCU_LOCKDEP_WARN(!rcu_is_watching(), "exception_enter didn't work");
}
@@ -825,8 +816,6 @@ NOKPROBE_SYMBOL(debug_exception_enter);
static void debug_exception_exit(struct pt_regs *regs)
{
- preempt_enable_no_resched();
-
if (!user_mode(regs))
rcu_nmi_exit();
--
2.7.4
The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 2194bc7c39610be7cabe7456c5f63a570604f015 Mon Sep 17 00:00:00 2001
From: Rajat Jain <rajatja(a)google.com>
Date: Mon, 6 Jul 2020 16:32:40 -0700
Subject: [PATCH] PCI: Add device even if driver attach failed
device_attach() returning failure indicates a driver error while trying to
probe the device. In such a scenario, the PCI device should still be added
in the system and be visible to the user.
When device_attach() fails, merely warn about it and keep the PCI device in
the system.
This partially reverts ab1a187bba5c ("PCI: Check device_attach() return
value always").
Link: https://lore.kernel.org/r/20200706233240.3245512-1-rajatja@google.com
Signed-off-by: Rajat Jain <rajatja(a)google.com>
Signed-off-by: Bjorn Helgaas <bhelgaas(a)google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org>
Cc: stable(a)vger.kernel.org # v4.6+
diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 8e40b3e6da77..3cef835b375f 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -322,12 +322,8 @@ void pci_bus_add_device(struct pci_dev *dev)
dev->match_driver = true;
retval = device_attach(&dev->dev);
- if (retval < 0 && retval != -EPROBE_DEFER) {
+ if (retval < 0 && retval != -EPROBE_DEFER)
pci_warn(dev, "device attach failed (%d)\n", retval);
- pci_proc_detach_device(dev);
- pci_remove_sysfs_dev_files(dev);
- return;
- }
pci_dev_assign_added(dev, true);
}