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authorMadhuparna Bhowmik <madhuparnabhowmik10@gmail.com>2020-04-30 21:32:05 +0530
committerMimi Zohar <zohar@linux.ibm.com>2020-05-07 21:36:32 -0400
commit770f60586d2af0590be263f55fd079226313922c (patch)
treec0b87532373b1f8135b090a9722328d018a5fb3d
parent2e3a34e9f409ebe83d1af7cd2f49fca7af97dfac (diff)
evm: Fix RCU list related warnings
This patch fixes the following warning and few other instances of traversal of evm_config_xattrnames list: [ 32.848432] ============================= [ 32.848707] WARNING: suspicious RCU usage [ 32.848966] 5.7.0-rc1-00006-ga8d5875ce5f0b #1 Not tainted [ 32.849308] ----------------------------- [ 32.849567] security/integrity/evm/evm_main.c:231 RCU-list traversed in non-reader section!! Since entries are only added to the list and never deleted, use list_for_each_entry_lockless() instead of list_for_each_entry_rcu for traversing the list. Also, add a relevant comment in evm_secfs.c to indicate this fact. Reported-by: kernel test robot <lkp@intel.com> Suggested-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com> Acked-by: Paul E. McKenney <paulmck@kernel.org> (RCU viewpoint) Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
-rw-r--r--security/integrity/evm/evm_crypto.c2
-rw-r--r--security/integrity/evm/evm_main.c4
-rw-r--r--security/integrity/evm/evm_secfs.c9
3 files changed, 11 insertions, 4 deletions
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index 77ad1e5a93e4..2e1597e59606 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -207,7 +207,7 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
data->hdr.length = crypto_shash_digestsize(desc->tfm);
error = -ENODATA;
- list_for_each_entry_rcu(xattr, &evm_config_xattrnames, list) {
+ list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
bool is_ima = false;
if (strcmp(xattr->name, XATTR_NAME_IMA) == 0)
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index d361d7fdafc4..0d36259b690d 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -97,7 +97,7 @@ static int evm_find_protected_xattrs(struct dentry *dentry)
if (!(inode->i_opflags & IOP_XATTR))
return -EOPNOTSUPP;
- list_for_each_entry_rcu(xattr, &evm_config_xattrnames, list) {
+ list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0);
if (error < 0) {
if (error == -ENODATA)
@@ -228,7 +228,7 @@ static int evm_protected_xattr(const char *req_xattr_name)
struct xattr_list *xattr;
namelen = strlen(req_xattr_name);
- list_for_each_entry_rcu(xattr, &evm_config_xattrnames, list) {
+ list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
if ((strlen(xattr->name) == namelen)
&& (strncmp(req_xattr_name, xattr->name, namelen) == 0)) {
found = 1;
diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c
index 39ad1038d45d..cfc3075769bb 100644
--- a/security/integrity/evm/evm_secfs.c
+++ b/security/integrity/evm/evm_secfs.c
@@ -232,7 +232,14 @@ static ssize_t evm_write_xattrs(struct file *file, const char __user *buf,
goto out;
}
- /* Guard against races in evm_read_xattrs */
+ /*
+ * xattr_list_mutex guards against races in evm_read_xattrs().
+ * Entries are only added to the evm_config_xattrnames list
+ * and never deleted. Therefore, the list is traversed
+ * using list_for_each_entry_lockless() without holding
+ * the mutex in evm_calc_hmac_or_hash(), evm_find_protected_xattrs()
+ * and evm_protected_xattr().
+ */
mutex_lock(&xattr_list_mutex);
list_for_each_entry(tmp, &evm_config_xattrnames, list) {
if (strcmp(xattr->name, tmp->name) == 0) {