From 65a0e100c8a6f8763a9c3bf2c0b361c8f436e42d Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sat, 16 Sep 2023 12:31:42 -0700 Subject: [PATCH] vm: fix move_vma() memory accounting being off Commit 408579cd627a ("mm: Update do_vmi_align_munmap() return semantics") seems to have updated one of the callers of do_vmi_munmap() incorrectly: it used to check for the error case (which didn't change: negative means error). That commit changed the check to the success case (which did change: before that commit, 0 was success, and 1 was "success and lock downgraded". After the change, it's always 0 for success, and the lock will have been released if requested). This didn't change any actual VM behavior _except_ for memory accounting when 'VM_ACCOUNT' was set on the vma. Which made the wrong return value test fairly subtle, since everything continues to work. Or rather - it continues to work but the "Committed memory" accounting goes all wonky (Committed_AS value in /proc/meminfo), and depending on settings that then causes problems much much later as the VM relies on bogus statistics for its heuristics. Revert that one line of the change back to the original logic. Fixes: 408579cd627a ("mm: Update do_vmi_align_munmap() return semantics") Reported-by: Christoph Biedl Reported-and-bisected-by: Michael Labiuk Cc: Bagas Sanjaya Cc: Liam R. Howlett Link: https://lore.kernel.org/all/1694366957@msgid.manchmal.in-ulm.de/ Signed-off-by: Linus Torvalds --- mm/mremap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/mremap.c b/mm/mremap.c index 056478c106ee..382e81c33fc4 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -715,7 +715,7 @@ static unsigned long move_vma(struct vm_area_struct *vma, } vma_iter_init(&vmi, mm, old_addr); - if (!do_vmi_munmap(&vmi, mm, old_addr, old_len, uf_unmap, false)) { + if (do_vmi_munmap(&vmi, mm, old_addr, old_len, uf_unmap, false) < 0) { /* OOM: unable to split vma, just get accounts right */ if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) vm_acct_memory(old_len >> PAGE_SHIFT); -- 2.42.0.rc0.30.gca81aba3b0