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Date: Thu, 04 Apr 2024 15:59:07 -0000
From: "tip-bot2 for Borislav Petkov (AMD)" <tip-bot2@linutronix.de>
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Subject:
 [tip: x86/urgent] x86/mce: Make sure to grab mce_sysfs_mutex in set_bank()
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>,  <stable@kernel.org>,
 x86@kernel.org, linux-kernel@vger.kernel.org
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The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     3ddf944b32f88741c303f0b21459dbb3872b8bc5
Gitweb:        https://git.kernel.org/tip/3ddf944b32f88741c303f0b21459dbb3872=
b8bc5
Author:        Borislav Petkov (AMD) <bp@alien8.de>
AuthorDate:    Wed, 13 Mar 2024 14:48:27 +01:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Thu, 04 Apr 2024 17:25:15 +02:00

x86/mce: Make sure to grab mce_sysfs_mutex in set_bank()

Modifying a MCA bank's MCA_CTL bits which control which error types to
be reported is done over

  /sys/devices/system/machinecheck/
  =E2=94=9C=E2=94=80=E2=94=80 machinecheck0
  =E2=94=82=C2=A0=C2=A0 =E2=94=9C=E2=94=80=E2=94=80 bank0
  =E2=94=82=C2=A0=C2=A0 =E2=94=9C=E2=94=80=E2=94=80 bank1
  =E2=94=82=C2=A0=C2=A0 =E2=94=9C=E2=94=80=E2=94=80 bank10
  =E2=94=82=C2=A0=C2=A0 =E2=94=9C=E2=94=80=E2=94=80 bank11
  ...

sysfs nodes by writing the new bit mask of events to enable.

When the write is accepted, the kernel deletes all current timers and
reinits all banks.

Doing that in parallel can lead to initializing a timer which is already
armed and in the timer wheel, i.e., in use already:

  ODEBUG: init active (active state 0) object: ffff888063a28000 object
  type: timer_list hint: mce_timer_fn+0x0/0x240 arch/x86/kernel/cpu/mce/core.=
c:2642
  WARNING: CPU: 0 PID: 8120 at lib/debugobjects.c:514
  debug_print_object+0x1a0/0x2a0 lib/debugobjects.c:514

Fix that by grabbing the sysfs mutex as the rest of the MCA sysfs code
does.

Reported by: Yue Sun <samsun1006219@gmail.com>
Reported by: xingwei lee <xrivendell7@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
Link: https://lore.kernel.org/r/CAEkJfYNiENwQY8yV1LYJ9LjJs%2Bx_-PqMv98gKig55=
=3D2vbzffRw@mail.gmail.com
---
 arch/x86/kernel/cpu/mce/core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index b5cc557..84d41be 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -2500,12 +2500,14 @@ static ssize_t set_bank(struct device *s, struct devi=
ce_attribute *attr,
 		return -EINVAL;
=20
 	b =3D &per_cpu(mce_banks_array, s->id)[bank];
-
 	if (!b->init)
 		return -ENODEV;
=20
 	b->ctl =3D new;
+
+	mutex_lock(&mce_sysfs_mutex);
 	mce_restart();
+	mutex_unlock(&mce_sysfs_mutex);
=20
 	return size;
 }