The patch titled
Subject: kernel/sysctl.c: warn when a clamped sysctl parameter is set out of range
has been added to the -mm tree. Its filename is
sysctl-warn-when-a-clamped-sysctl-parameter-is-set-out-of-range.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/sysctl-warn-when-a-clamped-sysctl-parameter-is-set-out-of-range.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/sysctl-warn-when-a-clamped-sysctl-parameter-is-set-out-of-range.patch
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------------------------------------------------------
From: Waiman Long <longman@xxxxxxxxxx>
Subject: kernel/sysctl.c: warn when a clamped sysctl parameter is set out of range
Even with clamped sysctl parameters, it is still not that straightforward
to figure out the exact range of those parameters. One may try to write
extreme parameter values to see if they get clamped. To make it easier, a
warning with the expected range will now be printed in the kernel ring
buffer when a clamped sysctl parameter receives an out of range value.
Link: http://lkml.kernel.org/r/1519926220-7453-5-git-send-email-longman@xxxxxxxxxx
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: "Luis R. Rodriguez" <mcgrof@xxxxxxxxxx>
Cc: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/sysctl.h | 3 ++
kernel/sysctl.c | 52 +++++++++++++++++++++++++++++++++------
2 files changed, 47 insertions(+), 8 deletions(-)
diff -puN include/linux/sysctl.h~sysctl-warn-when-a-clamped-sysctl-parameter-is-set-out-of-range include/linux/sysctl.h
--- a/include/linux/sysctl.h~sysctl-warn-when-a-clamped-sysctl-parameter-is-set-out-of-range
+++ a/include/linux/sysctl.h
@@ -130,11 +130,14 @@ struct ctl_table
* @CTL_FLAGS_CLAMP_RANGE: Set to indicate that the entry should be
* flexibly clamped to min/max range in case the user provided
* an incorrect value.
+ * @CTL_FLAGS_OOR_WARNED: Set to indicate that an out of range warning
+ * had been issued for that entry.
*
* At most 16 different flags will be allowed.
*/
enum ctl_table_flags {
CTL_FLAGS_CLAMP_RANGE = BIT(0),
+ CTL_FLAGS_OOR_WARNED = BIT(1),
};
struct ctl_node {
diff -puN kernel/sysctl.c~sysctl-warn-when-a-clamped-sysctl-parameter-is-set-out-of-range kernel/sysctl.c
--- a/kernel/sysctl.c~sysctl-warn-when-a-clamped-sysctl-parameter-is-set-out-of-range
+++ a/kernel/sysctl.c
@@ -2505,6 +2505,7 @@ static int proc_dointvec_minmax_sysadmin
* @min: pointer to minimum allowable value
* @max: pointer to maximum allowable value
* @flags: pointer to flags
+ * @name: sysctl parameter name
*
* The do_proc_dointvec_minmax_conv_param structure provides the
* minimum and maximum values for doing range checking for those sysctl
@@ -2514,31 +2515,50 @@ struct do_proc_dointvec_minmax_conv_para
int *min;
int *max;
uint16_t *flags;
+ const char *name;
};
+/* Out of range warning message */
+#define proc_ctl_warn(type, ...) \
+ pr_warn("Kernel parameter \"%s\" was set out of range [%" \
+ #type ", %" #type "], clamped to %" #type ".\n", __VA_ARGS__)
+
static int do_proc_dointvec_minmax_conv(bool *negp, unsigned long *lvalp,
int *valp,
int write, void *data)
{
struct do_proc_dointvec_minmax_conv_param *param = data;
+
if (write) {
int val = *negp ? -*lvalp : *lvalp;
+ bool clamped = false;
bool clamp = param->flags &&
(*param->flags & CTL_FLAGS_CLAMP_RANGE);
if (param->min && *param->min > val) {
- if (clamp)
+ if (clamp) {
val = *param->min;
- else
+ clamped = true;
+ } else {
return -EINVAL;
+ }
}
if (param->max && *param->max < val) {
- if (clamp)
+ if (clamp) {
val = *param->max;
- else
+ clamped = true;
+ } else {
return -EINVAL;
+ }
}
*valp = val;
+ if (clamped && param->name &&
+ !(*param->flags & CTL_FLAGS_OOR_WARNED)) {
+ proc_ctl_warn(d, param->name,
+ param->min ? *param->min : -INT_MAX,
+ param->max ? *param->max : INT_MAX, val);
+ *param->flags |= CTL_FLAGS_OOR_WARNED;
+ }
} else {
int val = *valp;
if (val < 0) {
@@ -2576,6 +2596,7 @@ int proc_dointvec_minmax(struct ctl_tabl
.min = (int *) table->extra1,
.max = (int *) table->extra2,
.flags = &table->flags,
+ .name = table->procname,
};
return do_proc_dointvec(table, write, buffer, lenp, ppos,
do_proc_dointvec_minmax_conv, ¶m);
@@ -2586,6 +2607,7 @@ int proc_dointvec_minmax(struct ctl_tabl
* @min: pointer to minimum allowable value
* @max: pointer to maximum allowable value
* @flags: pointer to flags
+ * @name: sysctl parameter name
*
* The do_proc_douintvec_minmax_conv_param structure provides the
* minimum and maximum values for doing range checking for those sysctl
@@ -2595,6 +2617,7 @@ struct do_proc_douintvec_minmax_conv_par
unsigned int *min;
unsigned int *max;
uint16_t *flags;
+ const char *name;
};
static int do_proc_douintvec_minmax_conv(unsigned long *lvalp,
@@ -2605,6 +2628,7 @@ static int do_proc_douintvec_minmax_conv
if (write) {
unsigned int val = *lvalp;
+ bool clamped = false;
bool clamp = param->flags &&
(*param->flags & CTL_FLAGS_CLAMP_RANGE);
@@ -2612,18 +2636,29 @@ static int do_proc_douintvec_minmax_conv
return -EINVAL;
if (param->min && *param->min > val) {
- if (clamp)
+ if (clamp) {
val = *param->min;
- else
+ clamped = true;
+ } else {
return -ERANGE;
+ }
}
if (param->max && *param->max < val) {
- if (clamp)
+ if (clamp) {
val = *param->max;
- else
+ clamped = true;
+ } else {
return -ERANGE;
+ }
}
*valp = val;
+ if (clamped && param->name &&
+ !(*param->flags & CTL_FLAGS_OOR_WARNED)) {
+ proc_ctl_warn(u, param->name,
+ param->min ? *param->min : 0,
+ param->max ? *param->max : UINT_MAX, val);
+ *param->flags |= CTL_FLAGS_OOR_WARNED;
+ }
} else {
unsigned int val = *valp;
*lvalp = (unsigned long) val;
@@ -2659,6 +2694,7 @@ int proc_douintvec_minmax(struct ctl_tab
.min = (unsigned int *) table->extra1,
.max = (unsigned int *) table->extra2,
.flags = &table->flags,
+ .name = table->procname,
};
return do_proc_douintvec(table, write, buffer, lenp, ppos,
do_proc_douintvec_minmax_conv, ¶m);
_
Patches currently in -mm which might be from longman@xxxxxxxxxx are
list_lru-prefetch-neighboring-list-entries-before-acquiring-lock.patch
proc-sysctl-fix-typo-in-sysctl_check_table_array.patch
sysctl-add-kdoc-comments-to-do_proc_douintvec_minmax_conv_param.patch
sysctl-add-flags-to-support-min-max-range-clamping.patch
sysctl-warn-when-a-clamped-sysctl-parameter-is-set-out-of-range.patch
ipc-clamp-msgmni-and-shmmni-to-the-real-ipcmni-limit.patch
ipc-clamp-semmni-to-the-real-ipcmni-limit.patch
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