On Wed, Jun 14, 2017 at 6:12 PM, Thomas Garnier <thgarnie@xxxxxxxxxx> wrote: > Ensure the address limit is a user-mode segment before returning to > user-mode. Otherwise a process can corrupt kernel-mode memory and elevate > privileges [1]. > > The set_fs function sets the TIF_SETFS flag to force a slow path on > return. In the slow path, the address limit is checked to be USER_DS if > needed. > > The addr_limit_user_check function is added as a cross-architecture > function to check the address limit. > > [1] https://bugs.chromium.org/p/project-zero/issues/detail?id=990 > > Signed-off-by: Thomas Garnier <thgarnie@xxxxxxxxxx> Thanks for reworking this series! The bad state correctly BUGs under the LKDTM test: [ 21.171586] lkdtm: Performing direct entry CORRUPT_USER_DS [ 21.172791] lkdtm: setting bad task size limit [ 21.173742] ------------[ cut here ]------------ [ 21.174641] kernel BUG at ./include/linux/syscalls.h:220! ... [ 21.193166] Call Trace: [ 21.193617] ? trace_hardirqs_on_thunk+0x1a/0x1c [ 21.194443] entry_SYSCALL64_slow_path+0x25/0x25 Tested-by: Kees Cook <keescook@xxxxxxxxxxxx> -Kees -- Kees Cook Pixel Security -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
