From: Madhuparna Bhowmik madhuparnabhowmik10@gmail.com
[ Upstream commit 770f60586d2af0590be263f55fd079226313922c ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- security/integrity/evm/evm_crypto.c | 2 +- security/integrity/evm/evm_main.c | 4 ++-- security/integrity/evm/evm_secfs.c | 9 ++++++++- 3 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c index f0878d81dcef..d20f5792761c 100644 --- a/security/integrity/evm/evm_crypto.c +++ b/security/integrity/evm/evm_crypto.c @@ -215,7 +215,7 @@ 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 7f3f54d89a6e..e11d860fdce4 100644 --- a/security/integrity/evm/evm_main.c +++ b/security/integrity/evm/evm_main.c @@ -102,7 +102,7 @@ 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) @@ -233,7 +233,7 @@ 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 77de71b7794c..f112ca593adc 100644 --- a/security/integrity/evm/evm_secfs.c +++ b/security/integrity/evm/evm_secfs.c @@ -237,7 +237,14 @@ 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) {