Messages in this thread Patch in this message | | | From | Kuniyuki Iwashima <> | Subject | [PATCH v1 net 06/16] sysctl: Add proc_douintvec_minmax_lockless(). | Date | Tue, 5 Jul 2022 22:21:20 -0700 |
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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, ¶m); } +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
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