From: Hugh Dickins Date: Tue, 20 Jun 2017 09:10:44 +0000 (-0700) Subject: mm: fix new crash in unmapped_area_topdown() X-Git-Tag: Ubuntu-5.13.0-19.19~13269 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=f4cb767d76cf7ee72f97dd76f6cfa6c76a5edc89;p=mirror_ubuntu-jammy-kernel.git mm: fix new crash in unmapped_area_topdown() Trinity gets kernel BUG at mm/mmap.c:1963! in about 3 minutes of mmap testing. That's the VM_BUG_ON(gap_end < gap_start) at the end of unmapped_area_topdown(). Linus points out how MAP_FIXED (which does not have to respect our stack guard gap intentions) could result in gap_end below gap_start there. Fix that, and the similar case in its alternative, unmapped_area(). Cc: stable@vger.kernel.org Fixes: 1be7107fbe18 ("mm: larger stack guard gap, between vmas") Reported-by: Dave Jones Debugged-by: Linus Torvalds Signed-off-by: Hugh Dickins Acked-by: Michal Hocko Signed-off-by: Linus Torvalds --- diff --git a/mm/mmap.c b/mm/mmap.c index 8e07976d5e47..290b77d9a01e 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1817,7 +1817,8 @@ check_current: /* Check if current node has a suitable gap */ if (gap_start > high_limit) return -ENOMEM; - if (gap_end >= low_limit && gap_end - gap_start >= length) + if (gap_end >= low_limit && + gap_end > gap_start && gap_end - gap_start >= length) goto found; /* Visit right subtree if it looks promising */ @@ -1920,7 +1921,8 @@ check_current: gap_end = vm_start_gap(vma); if (gap_end < low_limit) return -ENOMEM; - if (gap_start <= high_limit && gap_end - gap_start >= length) + if (gap_start <= high_limit && + gap_end > gap_start && gap_end - gap_start >= length) goto found; /* Visit left subtree if it looks promising */