[110/227] mm/hwpoison: fix error page recovered but reported "not recovered"

Commit Message

Andrew Morton March 22, 2022, 9:44 p.m. UTC

From: Naoya Horiguchi <[e-mail]>
Subject: mm/hwpoison: fix error page recovered but reported "not recovered"

When an uncorrected memory error is consumed there is a race between the
CMCI from the memory controller reporting an uncorrected error with a UCNA
signature, and the core reporting and SRAR signature machine check when
the data is about to be consumed.

If the CMCI wins that race, the page is marked poisoned when
uc_decode_notifier() calls memory_failure() and the machine check
processing code finds the page already poisoned.  It calls
kill_accessing_process() to make sure a SIGBUS is sent.  But returns the
wrong error code.

Console log looks like this:

[34775.674296] mce: Uncorrected hardware memory error in user-access at 3710b3400
[34775.675413] Memory failure: 0x3710b3: recovery action for dirty LRU page: Recovered
[34775.690310] Memory failure: 0x3710b3: already hardware poisoned
[34775.696247] Memory failure: 0x3710b3: Sending SIGBUS to einj_mem_uc:361438 due to hardware memory corruption
[34775.706072] mce: Memory error not recovered

kill_accessing_process() is supposed to return -EHWPOISON to notify that
SIGBUS is already set to the process and kill_me_maybe() doesn't have to
send it again.  But current code simply fails to do this, so fix it to
make sure to work as intended.  This change avoids the noise message
"Memory error not recovered" and skips duplicate SIGBUSs.

[[e-mail]: reword some parts of commit message]
Link: https://lkml.kernel.org/r/[e-mail]
Fixes: a3f5d80ea401 ("mm,hwpoison: send SIGBUS with error virutal address")
Signed-off-by: Naoya Horiguchi <[e-mail]>
Reported-by: Youquan Song <[e-mail]>
Cc: Tony Luck <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/memory-failure.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Patch

--- a/mm/memory-failure.c~mm-hwpoison-fix-error-page-recovered-but-reported-not-recovered
+++ a/mm/memory-failure.c
@@ -707,8 +707,10 @@  static int kill_accessing_process(struct
 			      (void *)&priv);
 	if (ret == 1 && priv.tk.addr)
 		kill_proc(&priv.tk, pfn, flags);
+	else
+		ret = 0;
 	mmap_read_unlock(p->mm);
-	return ret ? -EFAULT : -EHWPOISON;
+	return ret > 0 ? -EHWPOISON : -EFAULT;
 }
 
 static const char *action_name[] = {