Messages in this thread Patch in this message | | | From | Kuniyuki Iwashima <> | Subject | [PATCH v1 net 08/16] sysctl: Add proc_dointvec_jiffies_lockless(). | Date | Tue, 5 Jul 2022 22:21:22 -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_dointvec_jiffies() to use READ_ONCE()/WRITE_ONCE() internally to fix a data-race on the sysctl side. For now, proc_dointvec_jiffies() 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_jiffies() to a wrapper of proc_dointvec_jiffies_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_jiffies()'s document and adds proc_dointvec_jiffies_lockless()'s one so that no one will use proc_dointvec_jiffies() anymore.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> --- include/linux/sysctl.h | 1 + kernel/sysctl.c | 26 ++++++++++++++++++++------ 2 files changed, 21 insertions(+), 6 deletions(-)
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index c23b6beef748..8747dbc721f5 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -89,6 +89,7 @@ PROC_HANDLER(proc_douintvec_lockless); PROC_HANDLER(proc_dointvec_minmax_lockless); PROC_HANDLER(proc_douintvec_minmax_lockless); PROC_HANDLER(proc_doulongvec_minmax_lockless); +PROC_HANDLER(proc_dointvec_jiffies_lockless); /* * Register a set of sysctl names by calling register_sysctl_table diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 931ab58985f2..11a1ce837623 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1221,10 +1221,15 @@ static int do_proc_dointvec_jiffies_conv(bool *negp, unsigned long *lvalp, if (write) { if (*lvalp > INT_MAX / HZ) return 1; - *valp = *negp ? -(*lvalp*HZ) : (*lvalp*HZ); + + if (*negp) + WRITE_ONCE(*valp, -(*lvalp * HZ)); + else + WRITE_ONCE(*valp, *lvalp * HZ); } else { - int val = *valp; + int val = READ_ONCE(*valp); unsigned long lval; + if (val < 0) { *negp = true; lval = -(unsigned long)val; @@ -1286,7 +1291,8 @@ static int do_proc_dointvec_ms_jiffies_conv(bool *negp, unsigned long *lvalp, } /** - * proc_dointvec_jiffies - read a vector of integers as seconds + * proc_dointvec_jiffies_lockless - read/write a vector of integers as + * seconds locklessly * @table: the sysctl table * @write: %TRUE if this is a write to the sysctl file * @buffer: the user buffer @@ -1294,17 +1300,23 @@ static int do_proc_dointvec_ms_jiffies_conv(bool *negp, unsigned long *lvalp, * @ppos: file position * * Reads/writes up to table->maxlen/sizeof(unsigned int) integer - * values from/to the user buffer, treated as an ASCII string. + * values from/to the user buffer, treated as an ASCII string. * The values read are assumed to be in seconds, and are converted into * jiffies. * * Returns 0 on success. */ +int proc_dointvec_jiffies_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_dointvec_jiffies_conv, NULL); +} + int proc_dointvec_jiffies(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_dointvec_jiffies_conv,NULL); + return proc_dointvec_jiffies_lockless(table, write, buffer, lenp, ppos); } /** @@ -1552,6 +1564,7 @@ PROC_HANDLER_ENOSYS(proc_douintvec_lockless); PROC_HANDLER_ENOSYS(proc_dointvec_minmax_lockless); PROC_HANDLER_ENOSYS(proc_douintvec_minmax_lockless); PROC_HANDLER_ENOSYS(proc_doulongvec_minmax_lockless); +PROC_HANDLER_ENOSYS(proc_dointvec_jiffies_lockless); #endif /* CONFIG_PROC_SYSCTL */ @@ -2468,3 +2481,4 @@ EXPORT_SYMBOL(proc_douintvec_lockless); EXPORT_SYMBOL(proc_dointvec_minmax_lockless); EXPORT_SYMBOL_GPL(proc_douintvec_minmax_lockless); EXPORT_SYMBOL(proc_doulongvec_minmax_lockless); +EXPORT_SYMBOL(proc_dointvec_jiffies_lockless); -- 2.30.2
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