The patch titled
Subject: acct: fix accuracy loss for input value of encode_comp_t()
has been added to the -mm mm-nonmm-unstable branch. Its filename is
acct-fix-accuracy-loss-for-input-value-of-encode_comp_t.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/acct-fix-accuracy-loss-for-input-value-of-encode_comp_t.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Zheng Yejian <zhengyejian1@xxxxxxxxxx>
Subject: acct: fix accuracy loss for input value of encode_comp_t()
Date: Sat, 15 May 2021 22:06:30 +0800
Patch series "Fix encode_comp_t()".
Type conversion in encode_comp_t() may look a bit problematic.
This patch (of 2):
See calculation of ac_{u,s}time in fill_ac():
> ac->ac_utime = encode_comp_t(nsec_to_AHZ(pacct->ac_utime));
> ac->ac_stime = encode_comp_t(nsec_to_AHZ(pacct->ac_stime));
Return value of nsec_to_AHZ() is always type of 'u64', but it is handled
as type of 'unsigned long' in encode_comp_t, and accuracy loss would
happen on 32-bit platform when 'unsigned long' value is 32-bit-width.
So 'u64' value of encode_comp_t() may look better.
Link: https://lkml.kernel.org/r/20210515140631.369106-1-zhengyejian1@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20210515140631.369106-2-zhengyejian1@xxxxxxxxxx
Signed-off-by: Zheng Yejian <zhengyejian1@xxxxxxxxxx>
Cc: Hanjun Guo <guohanjun@xxxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> # build-tested
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Zhang Jinhao <zhangjinhao2@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/acct.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/kernel/acct.c~acct-fix-accuracy-loss-for-input-value-of-encode_comp_t
+++ a/kernel/acct.c
@@ -320,7 +320,7 @@ void acct_exit_ns(struct pid_namespace *
}
/*
- * encode an unsigned long into a comp_t
+ * encode an u64 into a comp_t
*
* This routine has been adopted from the encode_comp_t() function in
* the kern_acct.c file of the FreeBSD operating system. The encoding
@@ -331,7 +331,7 @@ void acct_exit_ns(struct pid_namespace *
#define EXPSIZE 3 /* Base 8 (3 bit) exponent. */
#define MAXFRACT ((1 << MANTSIZE) - 1) /* Maximum fractional value. */
-static comp_t encode_comp_t(unsigned long value)
+static comp_t encode_comp_t(u64 value)
{
int exp, rnd;
_
Patches currently in -mm which might be from zhengyejian1@xxxxxxxxxx are
acct-fix-accuracy-loss-for-input-value-of-encode_comp_t.patch
acct-fix-potential-integer-overflow-in-encode_comp_t.patch
