On Wed, Jan 11, 2023 at 4:31 AM Roberto Sassu
[off-list ref] wrote:

On Fri, 2023-01-06 at 16:14 -0500, Paul Moore wrote:

quoted

On Wed, Dec 21, 2022 at 9:10 AM Roberto Sassu
[off-list ref] wrote:

quoted

From: Roberto Sassu <roberto.sassu@huawei.com>

Commit 98de59bfe4b2f ("take calculation of final prot in
security_mmap_file() into a helper") moved the code to update prot with the
actual protection flags to be granted to the requestor by the kernel to a
helper called mmap_prot(). However, the patch didn't update the argument
passed to ima_file_mmap(), making it receive the requested prot instead of
the final computed prot.

A possible consequence is that files mmapped as executable might not be
measured/appraised if PROT_EXEC is not requested but subsequently added in
the final prot.

Replace prot with mmap_prot(file, prot) as the second argument of
ima_file_mmap() to restore the original behavior.

Cc: stable@vger.kernel.org
Fixes: 98de59bfe4b2 ("take calculation of final prot in security_mmap_file() into a helper")
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
 security/security.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/security.c b/security/security.c
index d1571900a8c7..0d2359d588a1 100644
--- a/security/security.c
+++ b/security/security.c

@@ -1666,7 +1666,7 @@ int security_mmap_file(struct file *file, unsigned long prot,
                                        mmap_prot(file, prot), flags);
        if (ret)
                return ret;
-       return ima_file_mmap(file, prot);
+       return ima_file_mmap(file, mmap_prot(file, prot));
 }

This seems like a reasonable fix, although as the original commit is
~10 years old at this point I am a little concerned about the impact
this might have on IMA.  Mimi, what do you think?

Beyond that, my only other comment would be to only call mmap_prot()
once and cache the results in a local variable.  You could also fix up
some of the ugly indentation crimes in security_mmap_file() while you
are at it, e.g. something like this:

Hi Paul

thanks for the comments. With the patch set to move IMA and EVM to the
LSM infrastructure we will be back to calling mmap_prot() only once,
but I guess we could do anyway, as the patch (if accepted) would be
likely backported to stable kernels.

I think there is value in fixing this now and keeping it separate from
the IMA-to-LSM work as they really are disjoint.

-- 
paul-moore.com