lsm: fix smack_inode_removexattr and xattr_getsecurity memleak (57e7ba04) · Commits · 戴 / test

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>

fs/xattr.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;
		}

security/smack/smack_lsm.c

+25 −30

Original line number	Diff line number	Diff line
		@@ -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
		*/
		@@ -1486,16 +1486,10 @@ 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.
		*/
		@@ -1515,14 +1509,15 @@ static int smack_inode_getsecurity(struct inode *inode,
		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);
		}

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