From 6df819a5c168ea51228e491d18fedd9cfbd38946 Mon Sep 17 00:00:00 2001 From: "Liam R. Howlett" Date: Thu, 31 Oct 2024 15:36:08 -0400 Subject: [PATCH] vma: detect infinite loop in vma tree There have been no reported infinite loops in the tree, but checking the detection of an infinite loop during validation is simple enough. Add the detection to the validate_mm() function so that error reports are clear and don't just report stalls. This does not protect against internal maple tree issues, but it does detect too many vmas being returned from the tree. The variance of +10 is to allow for the debugging output to be more useful for nearly correct counts. In the event of more than 10 over the map_count, the count will be set to -1 for easier identification of a potential infinite loop. Note that the mmap lock is held to ensure a consistent tree state during the validation process. Link: https://lkml.kernel.org/r/20241031193608.1965366-1-Liam.Howlett@oracle.com Signed-off-by: Liam R. Howlett Reviewed-by: David Hildenbrand Reviewed-by: Vlastimil Babka Cc: Lorenzo Stoakes Cc: Jann Horn Signed-off-by: Andrew Morton --- mm/vma.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/vma.c b/mm/vma.c index 68138e8c153e6..283e6bc4884f3 100644 --- a/mm/vma.c +++ b/mm/vma.c @@ -615,7 +615,10 @@ void validate_mm(struct mm_struct *mm) anon_vma_unlock_read(anon_vma); } #endif - i++; + if (++i > mm->map_count + 10) { + i = -1; + break; + } } if (i != mm->map_count) { pr_emerg("map_count %d vma iterator %d\n", mm->map_count, i); -- 2.50.1