Hi Greg and Sasha,
On Tue, 10 Aug 2021 16:45:34 +0000 SeongJae Park <sj38.park(a)gmail.com> wrote:
> From: SeongJae Park <sjpark(a)amazon.de>
>
> When running a test program, 'run_one()' checks if the program has the
> execution permission and fails if it doesn't. However, it's easy to
> mistakenly missing the permission, as some common tools like 'diff'
> don't support the permission change well[1]. Compared to that, making
> mistakes in the test program's path would only rare, as those are
> explicitly listed in 'TEST_PROGS'. Therefore, it might make more sense
> to resolve the situation on our own and run the program.
>
> For the reason, this commit makes the test program runner function to
> still print the warning message but try parsing the interpreter of the
> program and explicitly run it with the interpreter, in the case.
>
> [1] https://lore.kernel.org/mm-commits/YRJisBs9AunccCD4@kroah.com/
>
> Suggested-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org>
> Signed-off-by: SeongJae Park <sjpark(a)amazon.de>
This patch has merged into the mainline by the commit 303f8e2d0200
("selftests/kselftest/runner/run_one(): allow running non-executable files").
However, this patch has not added to v5.15.y, while there are some selftests
having no execution permission, including that for DAMON. As a result, the
selftests always fail unless this patch is manually applied. Could you please
add this patch to v5.15.y? I confirmed this patch can cleanly cherry-picked on
the latest v5.15.y.
Thanks,
SJ
[ Upstream commit 59f5ede3bc0f00eb856425f636dab0c10feb06d8 ]
The FPU usage related to task FPU management is either protected by
disabling interrupts (switch_to, return to user) or via fpregs_lock() which
is a wrapper around local_bh_disable(). When kernel code wants to use the
FPU then it has to check whether it is possible by calling irq_fpu_usable().
But the condition in irq_fpu_usable() is wrong. It allows FPU to be used
when:
!in_interrupt() || interrupted_user_mode() || interrupted_kernel_fpu_idle()
The latter is checking whether some other context already uses FPU in the
kernel, but if that's not the case then it allows FPU to be used
unconditionally even if the calling context interrupted a fpregs_lock()
critical region. If that happens then the FPU state of the interrupted
context becomes corrupted.
Allow in kernel FPU usage only when no other context has in kernel FPU
usage and either the calling context is not hard interrupt context or the
hard interrupt did not interrupt a local bottomhalf disabled region.
It's hard to find a proper Fixes tag as the condition was broken in one way
or the other for a very long time and the eager/lazy FPU changes caused a
lot of churn. Picked something remotely connected from the history.
This survived undetected for quite some time as FPU usage in interrupt
context is rare, but the recent changes to the random code unearthed it at
least on a kernel which had FPU debugging enabled. There is probably a
higher rate of silent corruption as not all issues can be detected by the
FPU debugging code. This will be addressed in a subsequent change.
Fixes: 5d2bd7009f30 ("x86, fpu: decouple non-lazy/eager fpu restore from xsave")
Reported-by: Filipe Manana <fdmanana(a)suse.com>
Signed-off-by: Thomas Gleixner <tglx(a)linutronix.de>
Tested-by: Filipe Manana <fdmanana(a)suse.com>
Reviewed-by: Borislav Petkov <bp(a)suse.de>
Cc: stable(a)vger.kernel.org
Cc: Can Sun <cansun(a)arista.com>
Link: https://lore.kernel.org/r/20220501193102.588689270@linutronix.de
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 571220ac8bea..835b948095cd 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -25,17 +25,7 @@
*/
union fpregs_state init_fpstate __read_mostly;
-/*
- * Track whether the kernel is using the FPU state
- * currently.
- *
- * This flag is used:
- *
- * - by IRQ context code to potentially use the FPU
- * if it's unused.
- *
- * - to debug kernel_fpu_begin()/end() correctness
- */
+/* Track in-kernel FPU usage */
static DEFINE_PER_CPU(bool, in_kernel_fpu);
/*
@@ -43,42 +33,37 @@ static DEFINE_PER_CPU(bool, in_kernel_fpu);
*/
DEFINE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx);
-static bool kernel_fpu_disabled(void)
-{
- return this_cpu_read(in_kernel_fpu);
-}
-
-static bool interrupted_kernel_fpu_idle(void)
-{
- return !kernel_fpu_disabled();
-}
-
-/*
- * Were we in user mode (or vm86 mode) when we were
- * interrupted?
- *
- * Doing kernel_fpu_begin/end() is ok if we are running
- * in an interrupt context from user mode - we'll just
- * save the FPU state as required.
- */
-static bool interrupted_user_mode(void)
-{
- struct pt_regs *regs = get_irq_regs();
- return regs && user_mode(regs);
-}
-
/*
* Can we use the FPU in kernel mode with the
* whole "kernel_fpu_begin/end()" sequence?
- *
- * It's always ok in process context (ie "not interrupt")
- * but it is sometimes ok even from an irq.
*/
bool irq_fpu_usable(void)
{
- return !in_interrupt() ||
- interrupted_user_mode() ||
- interrupted_kernel_fpu_idle();
+ if (WARN_ON_ONCE(in_nmi()))
+ return false;
+
+ /* In kernel FPU usage already active? */
+ if (this_cpu_read(in_kernel_fpu))
+ return false;
+
+ /*
+ * When not in NMI or hard interrupt context, FPU can be used in:
+ *
+ * - Task context except from within fpregs_lock()'ed critical
+ * regions.
+ *
+ * - Soft interrupt processing context which cannot happen
+ * while in a fpregs_lock()'ed critical region.
+ */
+ if (!in_irq())
+ return true;
+
+ /*
+ * In hard interrupt context it's safe when soft interrupts
+ * are enabled, which means the interrupt did not hit in
+ * a fpregs_lock()'ed critical region.
+ */
+ return !softirq_count();
}
EXPORT_SYMBOL(irq_fpu_usable);
From: Tze-nan Wu <Tze-nan.Wu(a)mediatek.com>
In ring_buffer_reset_online_cpus, the buffer_size_kb write operation
may permanently fail if the cpu_online_mask changes between two
for_each_online_buffer_cpu loops. The number of increases and decreases
on both cpu_buffer->resize_disabled and cpu_buffer->record_disabled may be
inconsistent, causing some CPUs to have non-zero values for these atomic
variables after the function returns.
This issue can be reproduced by "echo 0 > trace" while hotplugging cpu.
After reproducing success, we can find out buffer_size_kb will not be
functional anymore.
To prevent leaving 'resize_disabled' and 'record_disabled' non-zero after
ring_buffer_reset_online_cpus returns, we ensure that each atomic variable
has been set up before atomic_sub() to it.
Link: https://lore.kernel.org/linux-trace-kernel/20230426062027.17451-1-Tze-nan.W…
Cc: stable(a)vger.kernel.org
Cc: <mhiramat(a)kernel.org>
Cc: npiggin(a)gmail.com
Fixes: b23d7a5f4a07 ("ring-buffer: speed up buffer resets by avoiding synchronize_rcu for each CPU")
Reviewed-by: Cheng-Jui Wang <cheng-jui.wang(a)mediatek.com>
Signed-off-by: Tze-nan Wu <Tze-nan.Wu(a)mediatek.com>
Signed-off-by: Steven Rostedt (Google) <rostedt(a)goodmis.org>
---
kernel/trace/ring_buffer.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 58be5b409f72..9a0cb94c3972 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -5326,6 +5326,9 @@ void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
}
EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
+/* Flag to ensure proper resetting of atomic variables */
+#define RESET_BIT (1 << 30)
+
/**
* ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer
* @buffer: The ring buffer to reset a per cpu buffer of
@@ -5342,20 +5345,27 @@ void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
for_each_online_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
- atomic_inc(&cpu_buffer->resize_disabled);
+ atomic_add(RESET_BIT, &cpu_buffer->resize_disabled);
atomic_inc(&cpu_buffer->record_disabled);
}
/* Make sure all commits have finished */
synchronize_rcu();
- for_each_online_buffer_cpu(buffer, cpu) {
+ for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
+ /*
+ * If a CPU came online during the synchronize_rcu(), then
+ * ignore it.
+ */
+ if (!(atomic_read(&cpu_buffer->resize_disabled) & RESET_BIT))
+ continue;
+
reset_disabled_cpu_buffer(cpu_buffer);
atomic_dec(&cpu_buffer->record_disabled);
- atomic_dec(&cpu_buffer->resize_disabled);
+ atomic_sub(RESET_BIT, &cpu_buffer->resize_disabled);
}
mutex_unlock(&buffer->mutex);
--
2.39.2