Repost: Missing security_mmap_file() in remap_file_pages syscall
ztong at vt.edu
Mon Mar 25 17:33:51 UTC 2019
Dear Kernel Developers,
We’d like to bring this up for a discussion again.
Several months ago we posted an email discussing a case where remap_file_pages() has no security_mmap_file() check.
At that time we were told that do_mmap_pgoff() will base the new VMA permission on the old one.
But somehow we still think the check is needed, for the reason that the advisory could first do a
mmap() which can pass SELinux check then remap using a completely different file or region of file,
which could possibly pose a risk.
The original post is pasted below:
[1.] One line summary of the problem:
Possible missing security_mmap_file() in remap_file_pages
[2.] Full description of the problem/report:
We noticed remap_file_pages syscall uses do_mmap_pgoff without LSM check: security_mmap_file().
This system call passed user controllable parameters to do_mmap_pgoff().
We think that this LSM check should be added in order to be consistent with other cases,
in system call mmap_pgoff(), shmat(), they all have security_mmap_file() check before calling
[3.] Keywords: LSM check
[4.] Kernel information
[4.1] Kernel Version: 4.14.61
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