Currently proc_dobool expects a (bool *) in table->data, but sizeof(int)
in table->maxsize, because it uses do_proc_dointvec() directly.
This is unsafe for at least two reasons:
1. A sysctl table definition may use { .data = &variable, .maxsize =
sizeof(variable) }, not realizing that this makes the sysctl unusable
(see the Fixes: tag) and that they need to use the completely
counterintuitive sizeof(int) instead.
2. proc_dobool() will currently try to parse an array of values if given
.maxsize >= 2*sizeof(int), but will try to write values of type bool
by offsets of sizeof(int), so it will not work correctly with neither
an (int *) nor a (bool *). There is no .maxsize validation to prevent
this.
Fix this by:
1. Constraining proc_dobool() to allow only one value and .maxsize ==
sizeof(bool).
2. Wrapping the original struct ctl_table in a temporary one with .data
pointing to a local int variable and .maxsize set to sizeof(int) and
passing this one to proc_dointvec(), converting the value to/from
bool as needed (using proc_dou8vec_minmax() as an example).
3. Extending sysctl_check_table() to enforce proc_dobool() expectations.
4. Fixing the proc_dobool() docstring (it was just copy-pasted from
proc_douintvec, apparently...).
5. Converting all existing proc_dobool() users to set .maxsize to
sizeof(bool) instead of sizeof(int).
Fixes: 83efeeeb3d04 ("tty: Allow TIOCSTI to be disabled")
Fixes: a2071573d634 ("sysctl: introduce new proc handler proc_dobool")
Signed-off-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
---
fs/lockd/svc.c | 2 +-
fs/proc/proc_sysctl.c | 6 ++++++
kernel/sysctl.c | 43 ++++++++++++++++++++++++-------------------
mm/hugetlb_vmemmap.c | 2 +-
4 files changed, 32 insertions(+), 21 deletions(-)
diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c
index 59ef8a1f843f3..914ea1c3537d1 100644
--- a/fs/lockd/svc.c
+++ b/fs/lockd/svc.c
@@ -496,7 +496,7 @@ static struct ctl_table nlm_sysctls[] = {
{
.procname = "nsm_use_hostnames",
.data = &nsm_use_hostnames,
- .maxlen = sizeof(int),
+ .maxlen = sizeof(bool),
.mode = 0644,
.proc_handler = proc_dobool,
},
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 48f2d60bd78a2..436025e0f77a6 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -1124,6 +1124,11 @@ static int sysctl_check_table_array(const char *path, struct ctl_table *table)
err |= sysctl_err(path, table, "array not allowed");
}
+ if (table->proc_handler == proc_dobool) {
+ if (table->maxlen != sizeof(bool))
+ err |= sysctl_err(path, table, "array not allowed");
+ }
+
return err;
}
@@ -1136,6 +1141,7 @@ static int sysctl_check_table(const char *path, struct ctl_table *table)
err |= sysctl_err(path, entry, "Not a file");
if ((entry->proc_handler == proc_dostring) ||
+ (entry->proc_handler == proc_dobool) ||
(entry->proc_handler == proc_dointvec) ||
(entry->proc_handler == proc_douintvec) ||
(entry->proc_handler == proc_douintvec_minmax) ||
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 137d4abe3eda1..1c240d2c99bcb 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -425,21 +425,6 @@ 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)
-{
- if (write) {
- *(bool *)valp = *lvalp;
- } else {
- int val = *(bool *)valp;
-
- *lvalp = (unsigned long)val;
- *negp = false;
- }
- return 0;
-}
-
static int do_proc_dointvec_conv(bool *negp, unsigned long *lvalp,
int *valp,
int write, void *data)
@@ -710,16 +695,36 @@ int do_proc_douintvec(struct ctl_table *table, int write,
* @lenp: the size of the user 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.
+ * Reads/writes one integer value from/to the user buffer,
+ * treated as an ASCII string.
+ *
+ * table->data must point to a bool variable and table->maxlen must
+ * be sizeof(bool).
*
* Returns 0 on success.
*/
int proc_dobool(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);
+ struct ctl_table tmp;
+ bool *data = table->data;
+ int res, val;
+
+ /* Do not support arrays yet. */
+ if (table->maxlen != sizeof(bool))
+ return -EINVAL;
+
+ tmp = *table;
+ tmp.maxlen = sizeof(val);
+ tmp.data = &val;
+
+ val = READ_ONCE(*data);
+ res = proc_dointvec(&tmp, write, buffer, lenp, ppos);
+ if (res)
+ return res;
+ if (write)
+ WRITE_ONCE(*data, val);
+ return 0;
}
/**
diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index 45e93a545dd7e..a559037cce00c 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -581,7 +581,7 @@ static struct ctl_table hugetlb_vmemmap_sysctls[] = {
{
.procname = "hugetlb_optimize_vmemmap",
.data = &vmemmap_optimize_enabled,
- .maxlen = sizeof(int),
+ .maxlen = sizeof(vmemmap_optimize_enabled),
.mode = 0644,
.proc_handler = proc_dobool,
},
--
2.39.1
