forked from luck/tmp_suning_uos_patched
0e1a6ef2de
Currently the mmap_min_addr value can only be bypassed during mmap when the task has CAP_SYS_RAWIO. However, the mmap_min_addr sysctl value itself can be adjusted to 0 if euid == 0, allowing a bypass without CAP_SYS_RAWIO. This patch adds a check for the capability before allowing mmap_min_addr to be changed. Signed-off-by: Kees Cook <kees.cook@canonical.com> Acked-by: Serge Hallyn <serue@us.ibm.com> Signed-off-by: James Morris <jmorris@namei.org>
53 lines
1.3 KiB
C
53 lines
1.3 KiB
C
#include <linux/init.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/security.h>
|
|
#include <linux/sysctl.h>
|
|
|
|
/* amount of vm to protect from userspace access by both DAC and the LSM*/
|
|
unsigned long mmap_min_addr;
|
|
/* amount of vm to protect from userspace using CAP_SYS_RAWIO (DAC) */
|
|
unsigned long dac_mmap_min_addr = CONFIG_DEFAULT_MMAP_MIN_ADDR;
|
|
/* amount of vm to protect from userspace using the LSM = CONFIG_LSM_MMAP_MIN_ADDR */
|
|
|
|
/*
|
|
* Update mmap_min_addr = max(dac_mmap_min_addr, CONFIG_LSM_MMAP_MIN_ADDR)
|
|
*/
|
|
static void update_mmap_min_addr(void)
|
|
{
|
|
#ifdef CONFIG_LSM_MMAP_MIN_ADDR
|
|
if (dac_mmap_min_addr > CONFIG_LSM_MMAP_MIN_ADDR)
|
|
mmap_min_addr = dac_mmap_min_addr;
|
|
else
|
|
mmap_min_addr = CONFIG_LSM_MMAP_MIN_ADDR;
|
|
#else
|
|
mmap_min_addr = dac_mmap_min_addr;
|
|
#endif
|
|
}
|
|
|
|
/*
|
|
* sysctl handler which just sets dac_mmap_min_addr = the new value and then
|
|
* calls update_mmap_min_addr() so non MAP_FIXED hints get rounded properly
|
|
*/
|
|
int mmap_min_addr_handler(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp, loff_t *ppos)
|
|
{
|
|
int ret;
|
|
|
|
if (!capable(CAP_SYS_RAWIO))
|
|
return -EPERM;
|
|
|
|
ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
|
|
|
|
update_mmap_min_addr();
|
|
|
|
return ret;
|
|
}
|
|
|
|
int __init init_mmap_min_addr(void)
|
|
{
|
|
update_mmap_min_addr();
|
|
|
|
return 0;
|
|
}
|
|
pure_initcall(init_mmap_min_addr);
|