We have scripts which write to certain fields on 3.18 kernels but
this seems to be failing on 4.4 kernels. An entry which we write
to here is xfrm_aevent_rseqth which is u32.
echo 4294967295 > /proc/sys/net/core/xfrm_aevent_rseqth
Commit 230633d109e3 ("kernel/sysctl.c: detect overflows when
converting to int") prevented writing to sysctl entries when
integer overflow occurs. However, this does not apply to unsigned
integers.
Heinrich suggested that we introduce a new option to handle 64 bit
limits and set min as 0 and max as UINT_MAX. This might not work
as it leads to issues similar to __do_proc_doulongvec_minmax.
Alternatively, we would need to change the datatype of the entry
to 64 bit.
static int __do_proc_doulongvec_minmax(void *data, struct ctl_table
{
i = (unsigned long *) data; //This cast is causing to
read beyond the size of data (u32)
vleft = table->maxlen / sizeof(unsigned long); //vleft is 0
because maxlen is sizeof(u32) which is lesser than sizeof(unsigned
long) on x86_64.
Introduce a new proc handler proc_douintvec. Individual proc
entries will need to be updated to use the new handler.
Fixes: 230633d109e3 ("kernel/sysctl.c:detect overflows when converting to int")
Cc: Heinrich Schuchardt <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Subash Abhinov Kasiviswanathan <[email protected]>
---
include/linux/sysctl.h | 2 ++
kernel/sysctl.c | 42 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 44 insertions(+)
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 697e160..a4f7203 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -42,6 +42,8 @@ extern int proc_dostring(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
extern int proc_dointvec(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
+extern int proc_douintvec(struct ctl_table *, int,
+ void __user *, size_t *, loff_t *);
extern int proc_dointvec_minmax(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
extern int proc_dointvec_jiffies(struct ctl_table *, int,
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index b43d0b2..96437af 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2140,6 +2140,21 @@ static int do_proc_dointvec_conv(bool *negp, unsigned
long *lvalp,
return 0;
}
+static int do_proc_douintvec_conv(bool *negp, unsigned long *lvalp,
+ int *valp,
+ int write, void *data)
+{
+ if (write) {
+ if (*negp)
+ return -EINVAL;
+ *valp = *lvalp;
+ } else {
+ unsigned int val = *valp;
+ *lvalp = (unsigned long)val;
+ }
+ return 0;
+}
+
static const char proc_wspace_sep[] = { ' ', '\t', '\n' };
static int __do_proc_dointvec(void *tbl_data, struct ctl_table *table,
@@ -2263,6 +2278,26 @@ int proc_dointvec(struct ctl_table *table, int write,
NULL,NULL);
}
+/**
+ * proc_douintvec - read a vector of unsigned integers
+ * @table: the sysctl table
+ * @write: %TRUE if this is a write to the sysctl file
+ * @buffer: the user buffer
+ * @lenp: the size of the user buffer
+ * @ppos: file position
+ *
+ * Reads/writes up to table->maxlen/sizeof(unsigned int) unsigned integer
+ * values from/to the user buffer, treated as an ASCII string.
+ *
+ * Returns 0 on success.
+ */
+int proc_douintvec(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ return do_proc_dointvec(table,write,buffer,lenp,ppos,
+ do_proc_douintvec_conv, NULL);
+}
+
/*
* Taint values can only be increased
* This means we can safely use a temporary.
@@ -2858,6 +2893,12 @@ int proc_dointvec(struct ctl_table *table, int write,
return -ENOSYS;
}
+int proc_douintvec(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ return -ENOSYS;
+}
+
int proc_dointvec_minmax(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
@@ -2903,6 +2944,7 @@ int proc_doulongvec_ms_jiffies_minmax(struct ctl_table
*table, int write,
* exception granted :-)
*/
EXPORT_SYMBOL(proc_dointvec);
+EXPORT_SYMBOL(proc_douintvec);
EXPORT_SYMBOL(proc_dointvec_jiffies);
EXPORT_SYMBOL(proc_dointvec_minmax);
EXPORT_SYMBOL(proc_dointvec_userhz_jiffies);
--
1.9.1
