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selinux: move user accesses in selinuxfs out of locked regions 

If a user is accessing a file in selinuxfs with a pointer to a userspace
buffer that is backed by e.g. a userfaultfd, the userspace access can
stall indefinitely, which can block fsi->mutex if it is held.

For sel_read_policy(), remove the locking, since this method doesn't seem
to access anything that requires locking.

For sel_read_bool(), move the user access below the locked region.

For sel_write_bool() and sel_commit_bools_write(), move the user access
up above the locked region.

Cc: stable@vger.kernel.org
Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
[PM: removed an unused variable in sel_read_policy()]
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Jann Horn 2018-06-28 20:39:54 -04:00 committed by Paul Moore
parent d141136f52
commit 0da74120c5
1 changed files with 33 additions and 45 deletions
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78
security/selinux/selinuxfs.c
View File

@ -441,22 +441,16 @@ static int sel_release_policy(struct inode *inode, struct file *filp)
static ssize_t sel_read_policy(struct file *filp, char __user *buf,
size_t count, loff_t *ppos)
{
struct selinux_fs_info *fsi = file_inode(filp)->i_sb->s_fs_info;
struct policy_load_memory *plm = filp->private_data;
int ret;
mutex_lock(&fsi->mutex);
ret = avc_has_perm(&selinux_state,
current_sid(), SECINITSID_SECURITY,
SECCLASS_SECURITY, SECURITY__READ_POLICY, NULL);
if (ret)
goto out;
return ret;
ret = simple_read_from_buffer(buf, count, ppos, plm->data, plm->len);
out:
mutex_unlock(&fsi->mutex);
return ret;
return simple_read_from_buffer(buf, count, ppos, plm->data, plm->len);
}
static vm_fault_t sel_mmap_policy_fault(struct vm_fault *vmf)
@ -1188,25 +1182,29 @@ static ssize_t sel_read_bool(struct file *filep, char __user *buf,
ret = -EINVAL;
if (index >= fsi->bool_num || strcmp(name,
fsi->bool_pending_names[index]))
goto out;
goto out_unlock;
ret = -ENOMEM;
page = (char *)get_zeroed_page(GFP_KERNEL);
if (!page)
goto out;
goto out_unlock;
cur_enforcing = security_get_bool_value(fsi->state, index);
if (cur_enforcing < 0) {
ret = cur_enforcing;
goto out;
goto out_unlock;
}
length = scnprintf(page, PAGE_SIZE, "%d %d", cur_enforcing,
fsi->bool_pending_values[index]);
ret = simple_read_from_buffer(buf, count, ppos, page, length);
out:
mutex_unlock(&fsi->mutex);
ret = simple_read_from_buffer(buf, count, ppos, page, length);
out_free:
free_page((unsigned long)page);
return ret;
out_unlock:
mutex_unlock(&fsi->mutex);
goto out_free;
}
static ssize_t sel_write_bool(struct file *filep, const char __user *buf,
@ -1219,6 +1217,17 @@ static ssize_t sel_write_bool(struct file *filep, const char __user *buf,
unsigned index = file_inode(filep)->i_ino & SEL_INO_MASK;
const char *name = filep->f_path.dentry->d_name.name;
if (count >= PAGE_SIZE)
return -ENOMEM;
/* No partial writes. */
if (*ppos != 0)
return -EINVAL;
page = memdup_user_nul(buf, count);
if (IS_ERR(page))
return PTR_ERR(page);
mutex_lock(&fsi->mutex);
length = avc_has_perm(&selinux_state,
@ -1233,22 +1242,6 @@ static ssize_t sel_write_bool(struct file *filep, const char __user *buf,
fsi->bool_pending_names[index]))
goto out;
length = -ENOMEM;
if (count >= PAGE_SIZE)
goto out;
/* No partial writes. */
length = -EINVAL;
if (*ppos != 0)
goto out;
page = memdup_user_nul(buf, count);
if (IS_ERR(page)) {
length = PTR_ERR(page);
page = NULL;
goto out;
}
length = -EINVAL;
if (sscanf(page, "%d", &new_value) != 1)
goto out;
@ -1280,6 +1273,17 @@ static ssize_t sel_commit_bools_write(struct file *filep,
ssize_t length;
int new_value;
if (count >= PAGE_SIZE)
return -ENOMEM;
/* No partial writes. */
if (*ppos != 0)
return -EINVAL;
page = memdup_user_nul(buf, count);
if (IS_ERR(page))
return PTR_ERR(page);
mutex_lock(&fsi->mutex);
length = avc_has_perm(&selinux_state,
@ -1289,22 +1293,6 @@ static ssize_t sel_commit_bools_write(struct file *filep,
if (length)
goto out;
length = -ENOMEM;
if (count >= PAGE_SIZE)
goto out;
/* No partial writes. */
length = -EINVAL;
if (*ppos != 0)
goto out;
page = memdup_user_nul(buf, count);
if (IS_ERR(page)) {
length = PTR_ERR(page);
page = NULL;
goto out;
}
length = -EINVAL;
if (sscanf(page, "%d", &new_value) != 1)
goto out;