On Sat, Dec 22, 2018 at 1:14 PM Kevin 'ldir' Darbyshire-Bryant <[email protected]> wrote: > > > > > On 22 Dec 2018, at 18:28, Hauke Mehrtens <[email protected]> wrote: > > > > > > Hi Yousong, > > > > ASLR is currently not activated by default in OpenWrt, so the binary itself > > is not randomized. Activate CONFIG_PKG_ASLR_PIE to compile Openwrt with > > ASLR, but this increases the size of the binary. > > > > I haven't understood why some parts of the busybox binary and other > > binaries are mapped rwx, when I look into it with readelf no section is > > mapped rwx, but it looks like some sections are ending at an not page > > aligned offset and the next section starts directly after that. I assume > > that Linux merges the permissions when one page needs different permissions. > > > > I am still not sure if the common mips CPUs (24Kec, 74Kec) support > > restricting execution on pages anyway. > > > > Huake > > At the risk of going further down the rabbit hole/off topic, if you set the > cpu_has_rixi to 1 in > target/linux/ath79/patches-4.14/0014-MIPS-ath79-finetune-cpu-overrides.patch > and with PKG_ASLR_PIE [=y] Hauke mentioned on IRC that CPU_MIPSR2 in the kernel's Kconfig enables CPU_HAS_RIXI. grep the openwrt for RIXI to see what I mean.
HOWEVER, bcm47xx, ar71xx, ath79, mt7621, and a few others set cpu_has_rixi to 0. This is significant as several CPUs in OpenWrt like mt7620 should probably also be setting it if mt7621 is correct for example. This has to be bogus. I will definitely be run testing mt7621 device to see if anything happens. > > you get: > cat /proc/self/maps > 00400000-0047a000 r-xp 00000000 1f:03 1825 /bin/busybox > 00489000-0048a000 r--p 00079000 1f:03 1825 /bin/busybox > 0048a000-0048b000 rw-p 0007a000 1f:03 1825 /bin/busybox > 77e38000-77e5d000 r-xp 00000000 1f:03 2298 /lib/libgcc_s.so.1 > 77e5d000-77e5e000 rw-p 00015000 1f:03 2298 /lib/libgcc_s.so.1 > 77e5e000-77ef1000 r-xp 00000000 1f:03 2474 /lib/libc.so > 77f00000-77f02000 rw-p 00092000 1f:03 2474 /lib/libc.so > 77f02000-77f04000 rw-p 00000000 00:00 0 > 7f9bd000-7f9de000 rw-p 00000000 00:00 0 [stack] > 7fefb000-7fefc000 r-xp 00000000 00:00 0 > 7ff68000-7ff69000 r--p 00000000 00:00 0 [vvar] > 7ff69000-7ff6a000 r-xp 00000000 00:00 0 [vdso] > > > The archer hasn’t blown up…….yet > > Cheers, > > Kevin D-B > > 012C ACB2 28C6 C53E 9775 9123 B3A2 389B 9DE2 334A > > _______________________________________________ > openwrt-devel mailing list > [email protected] > https://lists.openwrt.org/mailman/listinfo/openwrt-devel _______________________________________________ openwrt-devel mailing list [email protected] https://lists.openwrt.org/mailman/listinfo/openwrt-devel
