On Tue, 19 Sep 2017, Casey Schaufler wrote:

Subject: [PATCH] fix security_release_secctx seems broken

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.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

Looks good to me.  I wonder why security_release_secctx was used in the 
first place? (it arrived via commit 42492594)

Konstantin: how did you trigger this?

I plan to send this to Linus for -rc4 unless anyone has objections.


-- 
James Morris
[off-list ref]

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