Messages in this thread Patch in this message | | | From | Kuniyuki Iwashima <> | Subject | [PATCH v1 net 02/16] sysctl: Add proc_dobool_lockless(). | Date | Tue, 5 Jul 2022 22:21:16 -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_dobool() to use READ_ONCE()/WRITE_ONCE() internally to fix a data-race on the sysctl side. For now, proc_dobool() 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_dobool() to a wrapper of proc_dobool_lockless(). When we fix a data-race in the other subsystem, we can explicitly set it as a handler.
Also, this patch removes proc_dobool()'s document and adds proc_dobool_lockless()'s one so that no one will use proc_dobool() anymore.
Fixes: a2071573d634 ("sysctl: introduce new proc handler proc_dobool") Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> --- CC: Jia He <hejianet@gmail.com> --- include/linux/sysctl.h | 2 ++ kernel/sysctl.c | 23 ++++++++++++++++------- 2 files changed, 18 insertions(+), 7 deletions(-)
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index 9beab3a4de3d..fcafc16abbad 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -83,6 +83,8 @@ PROC_HANDLER(proc_dointvec_ms_jiffies); PROC_HANDLER(proc_do_large_bitmap); PROC_HANDLER(proc_do_static_key); +PROC_HANDLER(proc_dobool_lockless); + /* * Register a set of sysctl names by calling register_sysctl_table * with an initialised array of struct ctl_table's. An entry with diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 1082c8bc5ba5..bc6fcc64eeaf 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -424,13 +424,12 @@ static void proc_put_char(void **buf, size_t *size, char c) } static int do_proc_dobool_conv(bool *negp, unsigned long *lvalp, - int *valp, - int write, void *data) + int *valp, int write, void *data) { if (write) { - *(bool *)valp = *lvalp; + WRITE_ONCE(*(bool *)valp, *lvalp); } else { - int val = *(bool *)valp; + int val = READ_ONCE(*(bool *)valp); *lvalp = (unsigned long)val; *negp = false; @@ -701,7 +700,7 @@ int do_proc_douintvec(struct ctl_table *table, int write, } /** - * proc_dobool - read/write a bool + * proc_dobool_lockless - read/write a bool locklessly * @table: the sysctl table * @write: %TRUE if this is a write to the sysctl file * @buffer: the user buffer @@ -713,13 +712,19 @@ int do_proc_douintvec(struct ctl_table *table, int write, * * Returns 0 on success. */ -int proc_dobool(struct ctl_table *table, int write, void *buffer, - size_t *lenp, loff_t *ppos) +int proc_dobool_lockless(struct ctl_table *table, int write, void *buffer, + size_t *lenp, loff_t *ppos) { return do_proc_dointvec(table, write, buffer, lenp, ppos, do_proc_dobool_conv, NULL); } +int proc_dobool(struct ctl_table *table, int write, void *buffer, + size_t *lenp, loff_t *ppos) +{ + return proc_dobool_lockless(table, write, buffer, lenp, ppos); +} + /** * proc_dointvec - read a vector of integers * @table: the sysctl table @@ -1497,6 +1502,8 @@ PROC_HANDLER_ENOSYS(proc_dointvec_ms_jiffies); PROC_HANDLER_ENOSYS(proc_do_cad_pid); PROC_HANDLER_ENOSYS(proc_do_large_bitmap); +PROC_HANDLER_ENOSYS(proc_dobool_lockless); + #endif /* CONFIG_PROC_SYSCTL */ #if defined(CONFIG_SYSCTL) @@ -2405,3 +2412,5 @@ EXPORT_SYMBOL(proc_dointvec_jiffies); EXPORT_SYMBOL(proc_dointvec_userhz_jiffies); EXPORT_SYMBOL(proc_dointvec_ms_jiffies); EXPORT_SYMBOL(proc_do_large_bitmap); + +EXPORT_SYMBOL(proc_dobool_lockless); -- 2.30.2
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