6.5-stable review patch. If anyone has any objections, please let me know.
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From: Linus Torvalds torvalds@linux-foundation.org
commit 3cec50490969afd4a76ccee441f747d869ccff77 upstream.
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 linux-kernel.bfrz@manchmal.in-ulm.de Reported-bisected-and-tested-by: Michael Labiuk michael.labiuk@virtuozzo.com Cc: Bagas Sanjaya bagasdotme@gmail.com Cc: Liam R. Howlett Liam.Howlett@oracle.com Link: https://lore.kernel.org/all/1694366957@msgid.manchmal.in-ulm.de/ Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Cc: Helge Deller deller@gmx.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/mremap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/mremap.c +++ b/mm/mremap.c @@ -715,7 +715,7 @@ static unsigned long move_vma(struct vm_ }
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);