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| author | Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com> | 2020-04-30 21:32:05 +0530 |
|---|---|---|
| committer | Mimi Zohar <zohar@linux.ibm.com> | 2020-05-07 21:36:32 -0400 |
| commit | 770f60586d2af0590be263f55fd079226313922c (patch) | |
| tree | c0b87532373b1f8135b090a9722328d018a5fb3d /security | |
| parent | 2e3a34e9f409ebe83d1af7cd2f49fca7af97dfac (diff) | |
| download | lwn-770f60586d2af0590be263f55fd079226313922c.tar.gz lwn-770f60586d2af0590be263f55fd079226313922c.zip | |
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>
Diffstat (limited to 'security')
| -rw-r--r-- | security/integrity/evm/evm_crypto.c | 2 | ||||
| -rw-r--r-- | security/integrity/evm/evm_main.c | 4 | ||||
| -rw-r--r-- | 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 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) { |