[PATCH 01/15] sysfs: Update sysfs_setxattr so it updates secdata under the sysfs_mutex

Eric W. Biederman
2009-11-08T07:30:40Z

From: Eric W. Biederman <ebiederm@maxwell.aristanetworks.com>

The sysfs_mutex is required to ensure updates are and will remain
atomic with respect to other inode iattr updates, that do not happen
through the filesystem.

Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
---
fs/sysfs/inode.c | 41 +++++++++++++++++++++++++++++------------
1 files changed, 29 insertions(+), 12 deletions(-)

diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index e28cecf..8a08250 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -122,23 +122,39 @@ int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
return error;
}

+static int sysfs_sd_setsecdata(struct sysfs_dirent *sd, void **secdata, u32 *secdata_len)
+{
+ struct sysfs_inode_attrs *iattrs;
+ void *old_secdata;
+ size_t old_secdata_len;
+
+ iattrs = sd->s_iattr;
+ if (!iattrs)
+ iattrs = sysfs_init_inode_attrs(sd);
+ if (!iattrs)
+ return -ENOMEM;
+
+ old_secdata = iattrs->ia_secdata;
+ old_secdata_len = iattrs->ia_secdata_len;
+
+ iattrs->ia_secdata = *secdata;
+ iattrs->ia_secdata_len = *secdata_len;
+
+ *secdata = old_secdata;
+ *secdata_len = old_secdata_len;
+ return 0;
+}
+
int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
size_t size, int flags)
{
struct sysfs_dirent *sd = dentry->d_fsdata;
- struct sysfs_inode_attrs *iattrs;
void *secdata;
int error;
u32 secdata_len = 0;

if (!sd)
return -EINVAL;
- if (!sd->s_iattr)
- sd->s_iattr = sysfs_init_inode_attrs(sd);
- if (!sd->s_iattr)
- return -ENOMEM;
-
- iattrs = sd->s_iattr;

if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
@@ -150,12 +166,13 @@ int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
&secdata, &secdata_len);
if (error)
goto out;
- if (iattrs->ia_secdata)
- security_release_secctx(iattrs->ia_secdata,
- iattrs->ia_secdata_len);
- iattrs->ia_secdata = secdata;
- iattrs->ia_secdata_len = secdata_len;

+ mutex_lock(&sysfs_mutex);
+ error = sysfs_sd_setsecdata(sd, &secdata, &secdata_len);
+ mutex_unlock(&sysfs_mutex);
+
+ if (secdata)
+ security_release_secctx(secdata, secdata_len);
} else
return -EINVAL;
out:
--
1.6.5.2.143.g8cc62