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lsm: fix smack_inode_removexattr and xattr_getsecurity memleak 

security_inode_getsecurity() provides the text string value
of a security attribute. It does not provide a "secctx".
The code in xattr_getsecurity() that calls security_inode_getsecurity()
and then calls security_release_secctx() happened to work because
SElinux and Smack treat the attribute and the secctx the same way.
It fails for cap_inode_getsecurity(), because that module has no
secctx that ever needs releasing. It turns out that Smack is the
one that's doing things wrong by not allocating memory when instructed
to do so by the "alloc" parameter.

The fix is simple enough. Change the security_release_secctx() to
kfree() because it isn't a secctx being returned by
security_inode_getsecurity(). Change Smack to allocate the string when
told to do so.

Note: this also fixes memory leaks for LSMs which implement
inode_getsecurity but not release_secctx, such as capabilities.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reported-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: stable@vger.kernel.org
Signed-off-by: James Morris <james.l.morris@oracle.com>
This commit is contained in:
Casey Schaufler 2017-09-19 09:39:08 -07:00 committed by James Morris
parent d81fa669e3
commit 57e7ba04d4
2 changed files with 28 additions and 33 deletions
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2
fs/xattr.c
View File

@ -250,7 +250,7 @@ xattr_getsecurity(struct inode *inode, const char *name, void *value,
}
memcpy(value, buffer, len);
out:
security_release_secctx(buffer, len);
kfree(buffer);
out_noalloc:
return len;
}

59
security/smack/smack_lsm.c
View File

@ -1473,7 +1473,7 @@ static int smack_inode_removexattr(struct dentry *dentry, const char *name)
* @inode: the object
* @name: attribute name
* @buffer: where to put the result
* @alloc: unused
* @alloc: duplicate memory
*
* Returns the size of the attribute or an error code
*/
@ -1486,43 +1486,38 @@ static int smack_inode_getsecurity(struct inode *inode,
struct super_block *sbp;
struct inode *ip = (struct inode *)inode;
struct smack_known *isp;
int ilen;
int rc = 0;
if (strcmp(name, XATTR_SMACK_SUFFIX) == 0) {
if (strcmp(name, XATTR_SMACK_SUFFIX) == 0)
isp = smk_of_inode(inode);
ilen = strlen(isp->smk_known);
*buffer = isp->smk_known;
return ilen;
else {
/*
* The rest of the Smack xattrs are only on sockets.
*/
sbp = ip->i_sb;
if (sbp->s_magic != SOCKFS_MAGIC)
return -EOPNOTSUPP;
sock = SOCKET_I(ip);
if (sock == NULL || sock->sk == NULL)
return -EOPNOTSUPP;
ssp = sock->sk->sk_security;
if (strcmp(name, XATTR_SMACK_IPIN) == 0)
isp = ssp->smk_in;
else if (strcmp(name, XATTR_SMACK_IPOUT) == 0)
isp = ssp->smk_out;
else
return -EOPNOTSUPP;
}
/*
* The rest of the Smack xattrs are only on sockets.
*/
sbp = ip->i_sb;
if (sbp->s_magic != SOCKFS_MAGIC)
return -EOPNOTSUPP;
sock = SOCKET_I(ip);
if (sock == NULL || sock->sk == NULL)
return -EOPNOTSUPP;
ssp = sock->sk->sk_security;
if (strcmp(name, XATTR_SMACK_IPIN) == 0)
isp = ssp->smk_in;
else if (strcmp(name, XATTR_SMACK_IPOUT) == 0)
isp = ssp->smk_out;
else
return -EOPNOTSUPP;
ilen = strlen(isp->smk_known);
if (rc == 0) {
*buffer = isp->smk_known;
rc = ilen;
if (alloc) {
*buffer = kstrdup(isp->smk_known, GFP_KERNEL);
if (*buffer == NULL)
return -ENOMEM;
}
return rc;
return strlen(isp->smk_known);
}