From 41032835dc2d489ec7841d7529f74f6389329cd3 Mon Sep 17 00:00:00 2001 From: "Jason A. Harmening" Date: Sun, 14 Feb 2021 18:47:22 -0800 Subject: [PATCH] Fix divide-by-zero panic when ASLR is enabled and superpages disabled When locating the anonymous memory region for a vm_map with ASLR enabled, we try to keep the slid base address aligned on a superpage boundary to minimize pagetable fragmentation and maximize the potential usage of superpage mappings. We can't (portably) do this if superpages have been disabled by loader tunable and pagesizes[1] is 0, and it would be less beneficial in that case anyway. PR: 253511 Reported by: johannes@jo-t.de MFC after: 1 week Reviewed by: kib Differential Revision: https://reviews.freebsd.org/D28678 --- sys/kern/imgact_elf.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/sys/kern/imgact_elf.c b/sys/kern/imgact_elf.c index dae11ab92a6..245894926ee 100644 --- a/sys/kern/imgact_elf.c +++ b/sys/kern/imgact_elf.c @@ -1287,7 +1287,8 @@ __CONCAT(exec_, __elfN(imgact))(struct image_params *imgp) maxv1 = maxv / 2 + addr / 2; MPASS(maxv1 >= addr); /* No overflow */ map->anon_loc = __CONCAT(rnd_, __elfN(base))(map, addr, maxv1, - MAXPAGESIZES > 1 ? pagesizes[1] : pagesizes[0]); + (MAXPAGESIZES > 1 && pagesizes[1] != 0) ? + pagesizes[1] : pagesizes[0]); } else { map->anon_loc = addr; } @@ -1297,7 +1298,7 @@ __CONCAT(exec_, __elfN(imgact))(struct image_params *imgp) if (interp != NULL) { VOP_UNLOCK(imgp->vp); if ((map->flags & MAP_ASLR) != 0) { - /* Assume that interpeter fits into 1/4 of AS */ + /* Assume that interpreter fits into 1/4 of AS */ maxv1 = maxv / 2 + addr / 2; MPASS(maxv1 >= addr); /* No overflow */ addr = __CONCAT(rnd_, __elfN(base))(map, addr,