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prctl_set_mm: refactor checks from validate_prctl_map

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Despite comment of validate_prctl_map claims there are no capability
checks, it is not completely true since commit 4d28df6152 ("prctl: Allow
local CAP_SYS_ADMIN changing exe_file").  Extract the check out of the
function and make the function perform purely arithmetic checks.

This patch should not change any behavior, it is mere refactoring for
following patch.

[akpm@linux-foundation.org: coding style fixes]
Link: http://lkml.kernel.org/r/20190502125203.24014-2-mkoutny@suse.com
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Mateusz Guzik <mguzik@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Michal Koutný 2019-05-31 22:30:16 -07:00 committed by Linus Torvalds
parent 8856ae4df3
commit 11bbd8b416
1 changed files with 25 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

51
kernel/sys.c
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@ -1882,13 +1882,14 @@ exit_err:
}
/*
* Check arithmetic relations of passed addresses.
*
* WARNING: we don't require any capability here so be very careful
* in what is allowed for modification from userspace.
*/
static int validate_prctl_map(struct prctl_mm_map *prctl_map)
static int validate_prctl_map_addr(struct prctl_mm_map *prctl_map)
{
unsigned long mmap_max_addr = TASK_SIZE;
struct mm_struct *mm = current->mm;
int error = -EINVAL, i;
static const unsigned char offsets[] = {
@ -1949,24 +1950,6 @@ static int validate_prctl_map(struct prctl_mm_map *prctl_map)
prctl_map->start_data))
goto out;
/*
* Someone is trying to cheat the auxv vector.
*/
if (prctl_map->auxv_size) {
if (!prctl_map->auxv || prctl_map->auxv_size > sizeof(mm->saved_auxv))
goto out;
}
/*
* Finally, make sure the caller has the rights to
* change /proc/pid/exe link: only local sys admin should
* be allowed to.
*/
if (prctl_map->exe_fd != (u32)-1) {
if (!ns_capable(current_user_ns(), CAP_SYS_ADMIN))
goto out;
}
error = 0;
out:
return error;
@ -1993,11 +1976,18 @@ static int prctl_set_mm_map(int opt, const void __user *addr, unsigned long data
if (copy_from_user(&prctl_map, addr, sizeof(prctl_map)))
return -EFAULT;
error = validate_prctl_map(&prctl_map);
error = validate_prctl_map_addr(&prctl_map);
if (error)
return error;
if (prctl_map.auxv_size) {
/*
* Someone is trying to cheat the auxv vector.
*/
if (!prctl_map.auxv ||
prctl_map.auxv_size > sizeof(mm->saved_auxv))
return -EINVAL;
memset(user_auxv, 0, sizeof(user_auxv));
if (copy_from_user(user_auxv,
(const void __user *)prctl_map.auxv,
@ -2010,6 +2000,14 @@ static int prctl_set_mm_map(int opt, const void __user *addr, unsigned long data
}
if (prctl_map.exe_fd != (u32)-1) {
/*
* Make sure the caller has the rights to
* change /proc/pid/exe link: only local sys admin should
* be allowed to.
*/
if (!ns_capable(current_user_ns(), CAP_SYS_ADMIN))
return -EINVAL;
error = prctl_set_mm_exe_file(mm, prctl_map.exe_fd);
if (error)
return error;
@ -2097,7 +2095,11 @@ static int prctl_set_mm(int opt, unsigned long addr,
unsigned long arg4, unsigned long arg5)
{
struct mm_struct *mm = current->mm;
struct prctl_mm_map prctl_map;
struct prctl_mm_map prctl_map = {
.auxv = NULL,
.auxv_size = 0,
.exe_fd = -1,
};
struct vm_area_struct *vma;
int error;
@ -2139,9 +2141,6 @@ static int prctl_set_mm(int opt, unsigned long addr,
prctl_map.arg_end = mm->arg_end;
prctl_map.env_start = mm->env_start;
prctl_map.env_end = mm->env_end;
prctl_map.auxv = NULL;
prctl_map.auxv_size = 0;
prctl_map.exe_fd = -1;
switch (opt) {
case PR_SET_MM_START_CODE:
@ -2181,7 +2180,7 @@ static int prctl_set_mm(int opt, unsigned long addr,
goto out;
}
error = validate_prctl_map(&prctl_map);
error = validate_prctl_map_addr(&prctl_map);
if (error)
goto out;