lkml.org 
[lkml]   [2022]   [Jul]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v1 net 06/16] sysctl: Add proc_douintvec_minmax_lockless().
Date
A sysctl variable is accessed concurrently, and there is always a chance of
data-race. So, all readers and writers need some basic protection to avoid
load/store-tearing.

This patch changes proc_douintvec_minmax() to use READ_ONCE()/WRITE_ONCE()
internally to fix a data-race on the sysctl side. For now,
proc_douintvec_minmax() itself is tolerant to a data-race, but we still
need to add annotations on the other subsystem's side.

In case we miss such fixes, this patch converts proc_douintvec_minmax() to
a wrapper of proc_douintvec_minmax_lockless(). When we fix a data-race in
the other subsystem, we can explicitly set it as a handler.

Also, this patch removes proc_douintvec_minmax()'s document and adds
proc_douintvec_minmax_lockless()'s one so that no one will use
proc_douintvec_minmax() anymore.

Fixes: 61d9b56a8920 ("sysctl: add unsigned int range support")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
CC: Luis R. Rodriguez <mcgrof@kernel.org>
---
include/linux/sysctl.h | 1 +
kernel/sysctl.c | 17 +++++++++++++----
2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 7f91cc625d56..830d1a8f21d4 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -87,6 +87,7 @@ PROC_HANDLER(proc_dobool_lockless);
PROC_HANDLER(proc_dointvec_lockless);
PROC_HANDLER(proc_douintvec_lockless);
PROC_HANDLER(proc_dointvec_minmax_lockless);
+PROC_HANDLER(proc_douintvec_minmax_lockless);

/*
* Register a set of sysctl names by calling register_sysctl_table
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index aead731ae74b..8ff57b8d1212 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -954,14 +954,15 @@ static int do_proc_douintvec_minmax_conv(unsigned long *lvalp,
(param->max && *param->max < tmp))
return -ERANGE;

- *valp = tmp;
+ WRITE_ONCE(*valp, tmp);
}

return 0;
}

/**
- * proc_douintvec_minmax - read a vector of unsigned ints with min/max values
+ * proc_douintvec_minmax_lockless - read/write a vector of unsigned ints
+ * with min/max values locklessly
* @table: the sysctl table
* @write: %TRUE if this is a write to the sysctl file
* @buffer: the user buffer
@@ -979,8 +980,8 @@ static int do_proc_douintvec_minmax_conv(unsigned long *lvalp,
*
* Returns 0 on success or -ERANGE on write when the range check fails.
*/
-int proc_douintvec_minmax(struct ctl_table *table, int write,
- void *buffer, size_t *lenp, loff_t *ppos)
+int proc_douintvec_minmax_lockless(struct ctl_table *table, int write,
+ void *buffer, size_t *lenp, loff_t *ppos)
{
struct do_proc_douintvec_minmax_conv_param param = {
.min = (unsigned int *) table->extra1,
@@ -990,6 +991,12 @@ int proc_douintvec_minmax(struct ctl_table *table, int write,
do_proc_douintvec_minmax_conv, &param);
}

+int proc_douintvec_minmax(struct ctl_table *table, int write,
+ void *buffer, size_t *lenp, loff_t *ppos)
+{
+ return proc_douintvec_minmax_lockless(table, write, buffer, lenp, ppos);
+}
+
/**
* proc_dou8vec_minmax - read a vector of unsigned chars with min/max values
* @table: the sysctl table
@@ -1532,6 +1539,7 @@ PROC_HANDLER_ENOSYS(proc_dobool_lockless);
PROC_HANDLER_ENOSYS(proc_dointvec_lockless);
PROC_HANDLER_ENOSYS(proc_douintvec_lockless);
PROC_HANDLER_ENOSYS(proc_dointvec_minmax_lockless);
+PROC_HANDLER_ENOSYS(proc_douintvec_minmax_lockless);

#endif /* CONFIG_PROC_SYSCTL */

@@ -2446,3 +2454,4 @@ EXPORT_SYMBOL(proc_dobool_lockless);
EXPORT_SYMBOL(proc_dointvec_lockless);
EXPORT_SYMBOL(proc_douintvec_lockless);
EXPORT_SYMBOL(proc_dointvec_minmax_lockless);
+EXPORT_SYMBOL_GPL(proc_douintvec_minmax_lockless);
--
2.30.2
\
 
 \ /
  Last update: 2022-07-06 07:24    [W:0.163 / U:0.424 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site