Kevin Darbyshire-Bryant 8f4841462c kernel: MIPS: math-emu Write-protect delay slot emulation pages ... Backport https://git.kernel.org/pub/scm/linux/kernel/git/mips/linux.git/commit/?id=adcc81f148d733b7e8e641300c5590a2cdc13bf3 "Mapping the delay slot emulation page as both writeable & executable presents a security risk, in that if an exploit can write to & jump into the page then it can be used as an easy way to execute arbitrary code. Prevent this by mapping the page read-only for userland, and using access_process_vm() with the FOLL_FORCE flag to write to it from mips_dsemul(). This will likely be less efficient due to copy_to_user_page() performing cache maintenance on a whole page, rather than a single line as in the previous use of flush_cache_sigtramp(). However this delay slot emulation code ought not to be running in any performance critical paths anyway so this isn't really a problem, and we can probably do better in copy_to_user_page() anyway in future. A major advantage of this approach is that the fix is small & simple to backport to stable kernels. Reported-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Paul Burton <paul.burton@mips.com> Fixes: 432c6bacbd0c ("MIPS: Use per-mm page to execute branch delay slot instructions")" Without patch: cat /proc/self/maps 00400000-0047a000 r-xp 00000000 1f:03 1823 /bin/busybox 00489000-0048a000 r-xp 00079000 1f:03 1823 /bin/busybox 0048a000-0048b000 rwxp 0007a000 1f:03 1823 /bin/busybox 77ec8000-77eed000 r-xp 00000000 1f:03 2296 /lib/libgcc_s.so.1 77eed000-77eee000 rwxp 00015000 1f:03 2296 /lib/libgcc_s.so.1 77eee000-77f81000 r-xp 00000000 1f:03 2470 /lib/libc.so 77f90000-77f92000 rwxp 00092000 1f:03 2470 /lib/libc.so 77f92000-77f94000 rwxp 00000000 00:00 0 7f946000-7f967000 rw-p 00000000 00:00 0 [stack] 7fefb000-7fefc000 rwxp 00000000 00:00 0 7ffac000-7ffad000 r--p 00000000 00:00 0 [vvar] 7ffad000-7ffae000 r-xp 00000000 00:00 0 [vdso] Patch applied: cat /proc/self/maps 00400000-0047a000 r-xp 00000000 1f:03 1825 /bin/busybox 00489000-0048a000 r-xp 00079000 1f:03 1825 /bin/busybox 0048a000-0048b000 rwxp 0007a000 1f:03 1825 /bin/busybox 77ed0000-77ef5000 r-xp 00000000 1f:03 2298 /lib/libgcc_s.so.1 77ef5000-77ef6000 rwxp 00015000 1f:03 2298 /lib/libgcc_s.so.1 77ef6000-77f89000 r-xp 00000000 1f:03 2474 /lib/libc.so 77f98000-77f9a000 rwxp 00092000 1f:03 2474 /lib/libc.so 77f9a000-77f9c000 rwxp 00000000 00:00 0 7fbed000-7fc0e000 rw-p 00000000 00:00 0 [stack] 7fefb000-7fefc000 r-xp 00000000 00:00 0 7fff6000-7fff7000 r--p 00000000 00:00 0 [vvar] 7fff7000-7fff8000 r-xp 00000000 00:00 0 [vdso] Note lack of write permission to 7fefb000-7fefc000 Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>		2018-12-24 21:52:08 +00:00
..
imagebuilder	imagebuilder: manifest function show stderr	2018-08-06 06:54:42 +02:00
linux	kernel: MIPS: math-emu Write-protect delay slot emulation pages	2018-12-24 21:52:08 +00:00
sdk	sdk: find kernel modules when KDIR is a symlink	2018-11-29 09:36:14 +01:00
toolchain	merge: etc: update remaining files	2017-12-08 19:41:18 +01:00
Config.in	build: add support for enabling the rootfs/boot partition size option via target feature	2018-09-03 12:06:24 +02:00
Makefile	build: make <subdir>/install opt-in, use it for target/ only	2017-02-09 13:51:35 +01:00