Messages in this thread Patch in this message | | | From | Kuniyuki Iwashima <> | Subject | [PATCH v1 net 03/16] sysctl: Add proc_dointvec_lockless(). | Date | Tue, 5 Jul 2022 22:21:17 -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() to use READ_ONCE()/WRITE_ONCE() internally to fix a data-race on the sysctl side. For now, proc_dointvec() 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() to a wrapper of proc_dointvec_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()'s document and adds proc_dointvec_lockless()'s one so that no one will use proc_dointvec() anymore.
While we are on it, we remove some trailing spaces.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> --- include/linux/sysctl.h | 1 + kernel/sysctl.c | 27 +++++++++++++++++++-------- 2 files changed, 20 insertions(+), 8 deletions(-)
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index fcafc16abbad..cb87919b5508 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -84,6 +84,7 @@ PROC_HANDLER(proc_do_large_bitmap); PROC_HANDLER(proc_do_static_key); PROC_HANDLER(proc_dobool_lockless); +PROC_HANDLER(proc_dointvec_lockless); /* * Register a set of sysctl names by calling register_sysctl_table diff --git a/kernel/sysctl.c b/kernel/sysctl.c index bc6fcc64eeaf..50d9b78aa0b3 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -445,14 +445,17 @@ static int do_proc_dointvec_conv(bool *negp, unsigned long *lvalp, if (*negp) { if (*lvalp > (unsigned long) INT_MAX + 1) return -EINVAL; - *valp = -*lvalp; + + WRITE_ONCE(*valp, -*lvalp); } else { if (*lvalp > (unsigned long) INT_MAX) return -EINVAL; - *valp = *lvalp; + + WRITE_ONCE(*valp, *lvalp); } } else { - int val = *valp; + int val = READ_ONCE(*valp); + if (val < 0) { *negp = true; *lvalp = -(unsigned long)val; @@ -491,12 +494,12 @@ static int __do_proc_dointvec(void *tbl_data, struct ctl_table *table, int *i, vleft, first = 1, err = 0; size_t left; char *p; - + if (!tbl_data || !table->maxlen || !*lenp || (*ppos && !write)) { *lenp = 0; return 0; } - + i = (int *) tbl_data; vleft = table->maxlen / sizeof(*i); left = *lenp; @@ -726,7 +729,7 @@ int proc_dobool(struct ctl_table *table, int write, void *buffer, } /** - * proc_dointvec - read a vector of integers + * proc_dointvec_lockless - read/write a vector of integers locklessly * @table: the sysctl table * @write: %TRUE if this is a write to the sysctl file * @buffer: the user buffer @@ -734,14 +737,20 @@ int proc_dobool(struct ctl_table *table, int write, void *buffer, * @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. * * Returns 0 on success. */ +int proc_dointvec_lockless(struct ctl_table *table, int write, void *buffer, + size_t *lenp, loff_t *ppos) +{ + return do_proc_dointvec(table, write, buffer, lenp, ppos, NULL, NULL); +} + int proc_dointvec(struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos) { - return do_proc_dointvec(table, write, buffer, lenp, ppos, NULL, NULL); + return proc_dointvec_lockless(table, write, buffer, lenp, ppos); } #ifdef CONFIG_COMPACTION @@ -1503,6 +1512,7 @@ PROC_HANDLER_ENOSYS(proc_do_cad_pid); PROC_HANDLER_ENOSYS(proc_do_large_bitmap); PROC_HANDLER_ENOSYS(proc_dobool_lockless); +PROC_HANDLER_ENOSYS(proc_dointvec_lockless); #endif /* CONFIG_PROC_SYSCTL */ @@ -2414,3 +2424,4 @@ EXPORT_SYMBOL(proc_dointvec_ms_jiffies); EXPORT_SYMBOL(proc_do_large_bitmap); EXPORT_SYMBOL(proc_dobool_lockless); +EXPORT_SYMBOL(proc_dointvec_lockless); -- 2.30.2
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