AuxXxilium/linux_dsm_epyc7002
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aio: mark AIO pseudo-fs noexec

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This ensures that do_mmap() won't implicitly make AIO memory mappings
executable if the READ_IMPLIES_EXEC personality flag is set.  Such
behavior is problematic because the security_mmap_file LSM hook doesn't
catch this case, potentially permitting an attacker to bypass a W^X
policy enforced by SELinux.

I have tested the patch on my machine.

To test the behavior, compile and run this:

    #define _GNU_SOURCE
    #include <unistd.h>
    #include <sys/personality.h>
    #include <linux/aio_abi.h>
    #include <err.h>
    #include <stdlib.h>
    #include <stdio.h>
    #include <sys/syscall.h>

    int main(void) {
        personality(READ_IMPLIES_EXEC);
        aio_context_t ctx = 0;
        if (syscall(__NR_io_setup, 1, &ctx))
            err(1, "io_setup");

        char cmd[1000];
        sprintf(cmd, "cat /proc/%d/maps | grep -F '/[aio]'",
            (int)getpid());
        system(cmd);
        return 0;
    }

In the output, "rw-s" is good, "rwxs" is bad.

Signed-off-by: Jann Horn <jann@thejh.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jann Horn 2016-09-16 00:31:22 +02:00 committed by Linus Torvalds
parent 024c7e3756
commit 22f6b4d34f
1 changed files with 6 additions and 1 deletions
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7
fs/aio.c
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@ -239,7 +239,12 @@ static struct dentry *aio_mount(struct file_system_type *fs_type,
static const struct dentry_operations ops = { static const struct dentry_operations ops = {
.d_dname = simple_dname, .d_dname = simple_dname,
}; };
return mount_pseudo(fs_type, "aio:", NULL, &ops, AIO_RING_MAGIC); struct dentry *root = mount_pseudo(fs_type, "aio:", NULL, &ops,
AIO_RING_MAGIC);
if (!IS_ERR(root))
root->d_sb->s_iflags |= SB_I_NOEXEC;
return root;
} }
/* aio_setup /* aio_setup