evm: Fix RCU list related warnings
[ Upstream commit 770f60586d
]
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>
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@ -209,7 +209,7 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
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data->hdr.length = crypto_shash_digestsize(desc->tfm);
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data->hdr.length = crypto_shash_digestsize(desc->tfm);
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error = -ENODATA;
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error = -ENODATA;
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list_for_each_entry_rcu(xattr, &evm_config_xattrnames, list) {
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list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
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bool is_ima = false;
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bool is_ima = false;
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if (strcmp(xattr->name, XATTR_NAME_IMA) == 0)
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if (strcmp(xattr->name, XATTR_NAME_IMA) == 0)
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@ -99,7 +99,7 @@ static int evm_find_protected_xattrs(struct dentry *dentry)
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if (!(inode->i_opflags & IOP_XATTR))
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if (!(inode->i_opflags & IOP_XATTR))
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return -EOPNOTSUPP;
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return -EOPNOTSUPP;
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list_for_each_entry_rcu(xattr, &evm_config_xattrnames, list) {
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list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
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error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0);
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error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0);
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if (error < 0) {
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if (error < 0) {
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if (error == -ENODATA)
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if (error == -ENODATA)
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@ -230,7 +230,7 @@ static int evm_protected_xattr(const char *req_xattr_name)
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struct xattr_list *xattr;
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struct xattr_list *xattr;
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namelen = strlen(req_xattr_name);
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namelen = strlen(req_xattr_name);
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list_for_each_entry_rcu(xattr, &evm_config_xattrnames, list) {
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list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
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if ((strlen(xattr->name) == namelen)
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if ((strlen(xattr->name) == namelen)
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&& (strncmp(req_xattr_name, xattr->name, namelen) == 0)) {
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&& (strncmp(req_xattr_name, xattr->name, namelen) == 0)) {
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found = 1;
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found = 1;
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@ -234,7 +234,14 @@ static ssize_t evm_write_xattrs(struct file *file, const char __user *buf,
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goto out;
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goto out;
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}
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}
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/* Guard against races in evm_read_xattrs */
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/*
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* xattr_list_mutex guards against races in evm_read_xattrs().
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* Entries are only added to the evm_config_xattrnames list
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* and never deleted. Therefore, the list is traversed
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* using list_for_each_entry_lockless() without holding
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* the mutex in evm_calc_hmac_or_hash(), evm_find_protected_xattrs()
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* and evm_protected_xattr().
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*/
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mutex_lock(&xattr_list_mutex);
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mutex_lock(&xattr_list_mutex);
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list_for_each_entry(tmp, &evm_config_xattrnames, list) {
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list_for_each_entry(tmp, &evm_config_xattrnames, list) {
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if (strcmp(xattr->name, tmp->name) == 0) {
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if (strcmp(xattr->name, tmp->name) == 0) {
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