Messages in this thread Patch in this message | | | From | Kuniyuki Iwashima <> | Subject | [PATCH v1 net 05/16] sysctl: Add proc_dointvec_minmax_lockless(). | Date | Tue, 5 Jul 2022 22:21:19 -0700 |
| |
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_dointvec_minmax() to use READ_ONCE()/WRITE_ONCE() internally to fix a data-race on the sysctl side. For now, proc_dointvec_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_dointvec_minmax() to a wrapper of proc_dointvec_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_dointvec_minmax()'s document and adds proc_dointvec_minmax_lockless()'s one so that no one will use proc_dointvec_minmax() anymore.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> --- include/linux/sysctl.h | 1 + kernel/sysctl.c | 19 +++++++++++++++---- 2 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index 770ee1833c25..7f91cc625d56 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -86,6 +86,7 @@ PROC_HANDLER(proc_do_static_key); PROC_HANDLER(proc_dobool_lockless); PROC_HANDLER(proc_dointvec_lockless); PROC_HANDLER(proc_douintvec_lockless); +PROC_HANDLER(proc_dointvec_minmax_lockless); /* * Register a set of sysctl names by calling register_sysctl_table diff --git a/kernel/sysctl.c b/kernel/sysctl.c index be8a7d912180..aead731ae74b 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -879,14 +879,16 @@ static int do_proc_dointvec_minmax_conv(bool *negp, unsigned long *lvalp, if ((param->min && *param->min > tmp) || (param->max && *param->max < tmp)) return -EINVAL; - *valp = tmp; + + WRITE_ONCE(*valp, tmp); } return 0; } /** - * proc_dointvec_minmax - read a vector of integers with min/max values + * proc_dointvec_minmax_lockless - read/write a vector of integers with + * min/max values locklessly * @table: the sysctl table * @write: %TRUE if this is a write to the sysctl file * @buffer: the user buffer @@ -901,8 +903,8 @@ static int do_proc_dointvec_minmax_conv(bool *negp, unsigned long *lvalp, * * Returns 0 on success or -EINVAL on write when the range check fails. */ -int proc_dointvec_minmax(struct ctl_table *table, int write, - void *buffer, size_t *lenp, loff_t *ppos) +int proc_dointvec_minmax_lockless(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) { struct do_proc_dointvec_minmax_conv_param param = { .min = (int *) table->extra1, @@ -912,6 +914,13 @@ int proc_dointvec_minmax(struct ctl_table *table, int write, do_proc_dointvec_minmax_conv, ¶m); } +int proc_dointvec_minmax(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + return proc_dointvec_minmax_lockless(table, write, buffer, + lenp, ppos); +} + /** * struct do_proc_douintvec_minmax_conv_param - proc_douintvec_minmax() range checking structure * @min: pointer to minimum allowable value @@ -1522,6 +1531,7 @@ PROC_HANDLER_ENOSYS(proc_do_large_bitmap); 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); #endif /* CONFIG_PROC_SYSCTL */ @@ -2435,3 +2445,4 @@ EXPORT_SYMBOL(proc_do_large_bitmap); EXPORT_SYMBOL(proc_dobool_lockless); EXPORT_SYMBOL(proc_dointvec_lockless); EXPORT_SYMBOL(proc_douintvec_lockless); +EXPORT_SYMBOL(proc_dointvec_minmax_lockless); -- 2.30.2
| |