5.15-stable patches

added patches:
	kexec-turn-all-kexec_mutex-acquisitions-into-trylocks.patch
	panic-kexec-make-__crash_kexec-nmi-safe.patch

diff --git a/queue-5.15/kexec-turn-all-kexec_mutex-acquisitions-into-trylocks.patch b/queue-5.15/kexec-turn-all-kexec_mutex-acquisitions-into-trylocks.patch
new file mode 100644 (file)
index 0000000..6be9a63
--- /dev/null
+++ b/queue-5.15/kexec-turn-all-kexec_mutex-acquisitions-into-trylocks.patch
@@ -0,0 +1,111 @@
+From 7bb5da0d490b2d836c5218f5186ee588d2145310 Mon Sep 17 00:00:00 2001
+From: Valentin Schneider <vschneid@redhat.com>
+Date: Thu, 30 Jun 2022 23:32:57 +0100
+Subject: kexec: turn all kexec_mutex acquisitions into trylocks
+
+From: Valentin Schneider <vschneid@redhat.com>
+
+commit 7bb5da0d490b2d836c5218f5186ee588d2145310 upstream.
+
+Patch series "kexec, panic: Making crash_kexec() NMI safe", v4.
+
+
+This patch (of 2):
+
+Most acquistions of kexec_mutex are done via mutex_trylock() - those were
+a direct "translation" from:
+
+  8c5a1cf0ad3a ("kexec: use a mutex for locking rather than xchg()")
+
+there have however been two additions since then that use mutex_lock():
+crash_get_memory_size() and crash_shrink_memory().
+
+A later commit will replace said mutex with an atomic variable, and
+locking operations will become atomic_cmpxchg().  Rather than having those
+mutex_lock() become while (atomic_cmpxchg(&lock, 0, 1)), turn them into
+trylocks that can return -EBUSY on acquisition failure.
+
+This does halve the printable size of the crash kernel, but that's still
+neighbouring 2G for 32bit kernels which should be ample enough.
+
+Link: https://lkml.kernel.org/r/20220630223258.4144112-1-vschneid@redhat.com
+Link: https://lkml.kernel.org/r/20220630223258.4144112-2-vschneid@redhat.com
+Signed-off-by: Valentin Schneider <vschneid@redhat.com>
+Cc: Arnd Bergmann <arnd@arndb.de>
+Cc: "Eric W . Biederman" <ebiederm@xmission.com>
+Cc: Juri Lelli <jlelli@redhat.com>
+Cc: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
+Cc: Miaohe Lin <linmiaohe@huawei.com>
+Cc: Petr Mladek <pmladek@suse.com>
+Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Cc: Thomas Gleixner <tglx@linutronix.de>
+Cc: Baoquan He <bhe@redhat.com>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Signed-off-by: Wen Yang <wenyang.linux@foxmail.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ include/linux/kexec.h |    2 +-
+ kernel/kexec_core.c   |   12 ++++++++----
+ kernel/ksysfs.c       |    7 ++++++-
+ 3 files changed, 15 insertions(+), 6 deletions(-)
+
+--- a/include/linux/kexec.h
++++ b/include/linux/kexec.h
+@@ -390,8 +390,8 @@ extern note_buf_t __percpu *crash_notes;
+ extern bool kexec_in_progress;
+ 
+ int crash_shrink_memory(unsigned long new_size);
+-size_t crash_get_memory_size(void);
+ void crash_free_reserved_phys_range(unsigned long begin, unsigned long end);
++ssize_t crash_get_memory_size(void);
+ 
+ void arch_kexec_protect_crashkres(void);
+ void arch_kexec_unprotect_crashkres(void);
+--- a/kernel/kexec_core.c
++++ b/kernel/kexec_core.c
+@@ -989,13 +989,16 @@ void crash_kexec(struct pt_regs *regs)
+       }
+ }
+ 
+-size_t crash_get_memory_size(void)
++ssize_t crash_get_memory_size(void)
+ {
+-      size_t size = 0;
++      ssize_t size = 0;
++
++      if (!mutex_trylock(&kexec_mutex))
++              return -EBUSY;
+ 
+-      mutex_lock(&kexec_mutex);
+       if (crashk_res.end != crashk_res.start)
+               size = resource_size(&crashk_res);
++
+       mutex_unlock(&kexec_mutex);
+       return size;
+ }
+@@ -1016,7 +1019,8 @@ int crash_shrink_memory(unsigned long ne
+       unsigned long old_size;
+       struct resource *ram_res;
+ 
+-      mutex_lock(&kexec_mutex);
++      if (!mutex_trylock(&kexec_mutex))
++              return -EBUSY;
+ 
+       if (kexec_crash_image) {
+               ret = -ENOENT;
+--- a/kernel/ksysfs.c
++++ b/kernel/ksysfs.c
+@@ -106,7 +106,12 @@ KERNEL_ATTR_RO(kexec_crash_loaded);
+ static ssize_t kexec_crash_size_show(struct kobject *kobj,
+                                      struct kobj_attribute *attr, char *buf)
+ {
+-      return sprintf(buf, "%zu\n", crash_get_memory_size());
++      ssize_t size = crash_get_memory_size();
++
++      if (size < 0)
++              return size;
++
++      return sprintf(buf, "%zd\n", size);
+ }
+ static ssize_t kexec_crash_size_store(struct kobject *kobj,
+                                  struct kobj_attribute *attr,

diff --git a/queue-5.15/panic-kexec-make-__crash_kexec-nmi-safe.patch b/queue-5.15/panic-kexec-make-__crash_kexec-nmi-safe.patch
new file mode 100644 (file)
index 0000000..8426414
--- /dev/null
+++ b/queue-5.15/panic-kexec-make-__crash_kexec-nmi-safe.patch
@@ -0,0 +1,228 @@
+From 05c6257433b7212f07a7e53479a8ab038fc1666a Mon Sep 17 00:00:00 2001
+From: Valentin Schneider <vschneid@redhat.com>
+Date: Thu, 30 Jun 2022 23:32:58 +0100
+Subject: panic, kexec: make __crash_kexec() NMI safe
+
+From: Valentin Schneider <vschneid@redhat.com>
+
+commit 05c6257433b7212f07a7e53479a8ab038fc1666a upstream.
+
+Attempting to get a crash dump out of a debug PREEMPT_RT kernel via an NMI
+panic() doesn't work.  The cause of that lies in the PREEMPT_RT definition
+of mutex_trylock():
+
+       if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES) && WARN_ON_ONCE(!in_task()))
+               return 0;
+
+This prevents an nmi_panic() from executing the main body of
+__crash_kexec() which does the actual kexec into the kdump kernel.  The
+warning and return are explained by:
+
+  6ce47fd961fa ("rtmutex: Warn if trylock is called from hard/softirq context")
+  [...]
+  The reasons for this are:
+
+      1) There is a potential deadlock in the slowpath
+
+      2) Another cpu which blocks on the rtmutex will boost the task
+        which allegedly locked the rtmutex, but that cannot work
+        because the hard/softirq context borrows the task context.
+
+Furthermore, grabbing the lock isn't NMI safe, so do away with kexec_mutex
+and replace it with an atomic variable.  This is somewhat overzealous as
+*some* callsites could keep using a mutex (e.g.  the sysfs-facing ones
+like crash_shrink_memory()), but this has the benefit of involving a
+single unified lock and preventing any future NMI-related surprises.
+
+Tested by triggering NMI panics via:
+
+  $ echo 1 > /proc/sys/kernel/panic_on_unrecovered_nmi
+  $ echo 1 > /proc/sys/kernel/unknown_nmi_panic
+  $ echo 1 > /proc/sys/kernel/panic
+
+  $ ipmitool power diag
+
+Link: https://lkml.kernel.org/r/20220630223258.4144112-3-vschneid@redhat.com
+Fixes: 6ce47fd961fa ("rtmutex: Warn if trylock is called from hard/softirq context")
+Signed-off-by: Valentin Schneider <vschneid@redhat.com>
+Cc: Arnd Bergmann <arnd@arndb.de>
+Cc: Baoquan He <bhe@redhat.com>
+Cc: "Eric W . Biederman" <ebiederm@xmission.com>
+Cc: Juri Lelli <jlelli@redhat.com>
+Cc: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
+Cc: Miaohe Lin <linmiaohe@huawei.com>
+Cc: Petr Mladek <pmladek@suse.com>
+Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Cc: Thomas Gleixner <tglx@linutronix.de>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Signed-off-by: Wen Yang <wenyang.linux@foxmail.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ kernel/kexec.c          |   11 ++++-------
+ kernel/kexec_core.c     |   20 ++++++++++----------
+ kernel/kexec_file.c     |    4 ++--
+ kernel/kexec_internal.h |   15 ++++++++++++++-
+ 4 files changed, 30 insertions(+), 20 deletions(-)
+
+--- a/kernel/kexec.c
++++ b/kernel/kexec.c
+@@ -93,13 +93,10 @@ static int do_kexec_load(unsigned long e
+ 
+       /*
+        * Because we write directly to the reserved memory region when loading
+-       * crash kernels we need a mutex here to prevent multiple crash kernels
+-       * from attempting to load simultaneously, and to prevent a crash kernel
+-       * from loading over the top of a in use crash kernel.
+-       *
+-       * KISS: always take the mutex.
++       * crash kernels we need a serialization here to prevent multiple crash
++       * kernels from attempting to load simultaneously.
+        */
+-      if (!mutex_trylock(&kexec_mutex))
++      if (!kexec_trylock())
+               return -EBUSY;
+ 
+       if (flags & KEXEC_ON_CRASH) {
+@@ -165,7 +162,7 @@ out:
+ 
+       kimage_free(image);
+ out_unlock:
+-      mutex_unlock(&kexec_mutex);
++      kexec_unlock();
+       return ret;
+ }
+ 
+--- a/kernel/kexec_core.c
++++ b/kernel/kexec_core.c
+@@ -46,7 +46,7 @@
+ #include <crypto/hash.h>
+ #include "kexec_internal.h"
+ 
+-DEFINE_MUTEX(kexec_mutex);
++atomic_t __kexec_lock = ATOMIC_INIT(0);
+ 
+ /* Per cpu memory for storing cpu states in case of system crash. */
+ note_buf_t __percpu *crash_notes;
+@@ -944,7 +944,7 @@ int kexec_load_disabled;
+  */
+ void __noclone __crash_kexec(struct pt_regs *regs)
+ {
+-      /* Take the kexec_mutex here to prevent sys_kexec_load
++      /* Take the kexec_lock here to prevent sys_kexec_load
+        * running on one cpu from replacing the crash kernel
+        * we are using after a panic on a different cpu.
+        *
+@@ -952,7 +952,7 @@ void __noclone __crash_kexec(struct pt_r
+        * of memory the xchg(&kexec_crash_image) would be
+        * sufficient.  But since I reuse the memory...
+        */
+-      if (mutex_trylock(&kexec_mutex)) {
++      if (kexec_trylock()) {
+               if (kexec_crash_image) {
+                       struct pt_regs fixed_regs;
+ 
+@@ -961,7 +961,7 @@ void __noclone __crash_kexec(struct pt_r
+                       machine_crash_shutdown(&fixed_regs);
+                       machine_kexec(kexec_crash_image);
+               }
+-              mutex_unlock(&kexec_mutex);
++              kexec_unlock();
+       }
+ }
+ STACK_FRAME_NON_STANDARD(__crash_kexec);
+@@ -993,13 +993,13 @@ ssize_t crash_get_memory_size(void)
+ {
+       ssize_t size = 0;
+ 
+-      if (!mutex_trylock(&kexec_mutex))
++      if (!kexec_trylock())
+               return -EBUSY;
+ 
+       if (crashk_res.end != crashk_res.start)
+               size = resource_size(&crashk_res);
+ 
+-      mutex_unlock(&kexec_mutex);
++      kexec_unlock();
+       return size;
+ }
+ 
+@@ -1019,7 +1019,7 @@ int crash_shrink_memory(unsigned long ne
+       unsigned long old_size;
+       struct resource *ram_res;
+ 
+-      if (!mutex_trylock(&kexec_mutex))
++      if (!kexec_trylock())
+               return -EBUSY;
+ 
+       if (kexec_crash_image) {
+@@ -1058,7 +1058,7 @@ int crash_shrink_memory(unsigned long ne
+       insert_resource(&iomem_resource, ram_res);
+ 
+ unlock:
+-      mutex_unlock(&kexec_mutex);
++      kexec_unlock();
+       return ret;
+ }
+ 
+@@ -1130,7 +1130,7 @@ int kernel_kexec(void)
+ {
+       int error = 0;
+ 
+-      if (!mutex_trylock(&kexec_mutex))
++      if (!kexec_trylock())
+               return -EBUSY;
+       if (!kexec_image) {
+               error = -EINVAL;
+@@ -1206,7 +1206,7 @@ int kernel_kexec(void)
+ #endif
+ 
+  Unlock:
+-      mutex_unlock(&kexec_mutex);
++      kexec_unlock();
+       return error;
+ }
+ 
+--- a/kernel/kexec_file.c
++++ b/kernel/kexec_file.c
+@@ -343,7 +343,7 @@ SYSCALL_DEFINE5(kexec_file_load, int, ke
+ 
+       image = NULL;
+ 
+-      if (!mutex_trylock(&kexec_mutex))
++      if (!kexec_trylock())
+               return -EBUSY;
+ 
+       dest_image = &kexec_image;
+@@ -415,7 +415,7 @@ out:
+       if ((flags & KEXEC_FILE_ON_CRASH) && kexec_crash_image)
+               arch_kexec_protect_crashkres();
+ 
+-      mutex_unlock(&kexec_mutex);
++      kexec_unlock();
+       kimage_free(image);
+       return ret;
+ }
+--- a/kernel/kexec_internal.h
++++ b/kernel/kexec_internal.h
+@@ -13,7 +13,20 @@ void kimage_terminate(struct kimage *ima
+ int kimage_is_destination_range(struct kimage *image,
+                               unsigned long start, unsigned long end);
+ 
+-extern struct mutex kexec_mutex;
++/*
++ * Whatever is used to serialize accesses to the kexec_crash_image needs to be
++ * NMI safe, as __crash_kexec() can happen during nmi_panic(), so here we use a
++ * "simple" atomic variable that is acquired with a cmpxchg().
++ */
++extern atomic_t __kexec_lock;
++static inline bool kexec_trylock(void)
++{
++      return atomic_cmpxchg_acquire(&__kexec_lock, 0, 1) == 0;
++}
++static inline void kexec_unlock(void)
++{
++      atomic_set_release(&__kexec_lock, 0);
++}
+ 
+ #ifdef CONFIG_KEXEC_FILE
+ #include <linux/purgatory.h>

diff --git a/queue-5.15/series b/queue-5.15/series
index 9ddfedfa0cdf7018f329693432ff56c4e09e2463..5c0d261ba9110c2b09fb02e31ab909382cbab4b0 100644 (file)
--- a/queue-5.15/series
+++ b/queue-5.15/series
@@ -84,3 +84,5 @@ nvme-pci-add-nvme_quirk_bogus_nid-for-t-force-z330-s.patch
 cgroup-cpuset-skip-spread-flags-update-on-v2.patch
 cgroup-cpuset-make-cpuset_fork-handle-clone_into_cgr.patch
 cgroup-cpuset-add-cpuset_can_fork-and-cpuset_cancel_fork-methods.patch
+kexec-turn-all-kexec_mutex-acquisitions-into-trylocks.patch
+panic-kexec-make-__crash_kexec-nmi-safe.patch