checkreqprot data member in selinux_state struct is accessed directly by
SELinux functions to get and set. This could cause unexpected read or
write access to this data member due to compiler optimizations and/or
compiler's reordering of access to this field.
Add helper functions to get and set checkreqprot data member in
selinux_state struct. These helper functions use READ_ONCE and
WRITE_ONCE macros to ensure atomic read or write of memory for
this data member.
Signed-off-by: Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx>
Suggested-by: Stephen Smalley <stephen.smalley.work@xxxxxxxxx>
---
security/selinux/hooks.c | 6 +++---
security/selinux/include/security.h | 10 ++++++++++
security/selinux/selinuxfs.c | 5 +++--
3 files changed, 16 insertions(+), 5 deletions(-)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 6210e98219a5..25a36a3e6bed 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3718,7 +3718,7 @@ static int selinux_mmap_file(struct file *file, unsigned long reqprot,
return rc;
}
- if (selinux_state.checkreqprot)
+ if (checkreqprot_enabled(&selinux_state))
prot = reqprot;
return file_map_prot_check(file, prot,
@@ -3732,7 +3732,7 @@ static int selinux_file_mprotect(struct vm_area_struct *vma,
const struct cred *cred = current_cred();
u32 sid = cred_sid(cred);
- if (selinux_state.checkreqprot)
+ if (checkreqprot_enabled(&selinux_state))
prot = reqprot;
if (default_noexec &&
@@ -7234,7 +7234,7 @@ static __init int selinux_init(void)
memset(&selinux_state, 0, sizeof(selinux_state));
enforcing_set(&selinux_state, selinux_enforcing_boot);
- selinux_state.checkreqprot = selinux_checkreqprot_boot;
+ checkreqprot_set(&selinux_state, selinux_checkreqprot_boot);
selinux_avc_init(&selinux_state.avc);
mutex_init(&selinux_state.status_lock);
mutex_init(&selinux_state.policy_mutex);
diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index cbdd3c7aff8b..cc29177c8858 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -143,6 +143,16 @@ static inline void enforcing_set(struct selinux_state *state, bool value)
}
#endif
+static inline bool checkreqprot_enabled(const struct selinux_state *state)
+{
+ return READ_ONCE(state->checkreqprot);
+}
+
+static inline void checkreqprot_set(struct selinux_state *state, bool value)
+{
+ WRITE_ONCE(state->checkreqprot, value);
+}
+
#ifdef CONFIG_SECURITY_SELINUX_DISABLE
static inline bool selinux_disabled(struct selinux_state *state)
{
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 45e9efa9bf5b..540bfa078877 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -717,7 +717,8 @@ static ssize_t sel_read_checkreqprot(struct file *filp, char __user *buf,
char tmpbuf[TMPBUFLEN];
ssize_t length;
- length = scnprintf(tmpbuf, TMPBUFLEN, "%u", fsi->state->checkreqprot);
+ length = scnprintf(tmpbuf, TMPBUFLEN, "%u",
+ checkreqprot_enabled(fsi->state));
return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
}
@@ -759,7 +760,7 @@ static ssize_t sel_write_checkreqprot(struct file *file, const char __user *buf,
comm, current->pid);
}
- fsi->state->checkreqprot = new_value ? 1 : 0;
+ checkreqprot_set(fsi->state, (new_value ? 1 : 0));
length = count;
out:
kfree(page);
--
2.28.0
