From: Vlastimil Babka vbabka@suse.cz
commit 6f12be792fde994ed934168f93c2a0d2a0cf0bc5 upstream.
Since 6.1 we have noticed random rpm install failures that were tracked to mremap() returning -ENOMEM and to commit ca3d76b0aa80 ("mm: add merging after mremap resize").
The problem occurs when mremap() expands a VMA in place, but using an starting address that's not vma->vm_start, but somewhere in the middle. The extension_pgoff calculation introduced by the commit is wrong in that case, so vma_merge() fails due to pgoffs not being compatible. Fix the calculation.
By the way it seems that the situations, where rpm now expands a vma from the middle, were made possible also due to that commit, thanks to the improved vma merging. Yet it should work just fine, except for the buggy calculation.
Link: https://lkml.kernel.org/r/20221216163227.24648-1-vbabka@suse.cz Reported-by: Jiri Slaby jirislaby@kernel.org Link: https://bugzilla.suse.com/show_bug.cgi?id=1206359 Fixes: ca3d76b0aa80 ("mm: add merging after mremap resize") Signed-off-by: Vlastimil Babka vbabka@suse.cz Cc: Jakub Matěna matenajakub@gmail.com Cc: "Kirill A . Shutemov" kirill@shutemov.name Cc: Liam Howlett liam.howlett@oracle.com Cc: Matthew Wilcox willy@infradead.org Cc: Mel Gorman mgorman@techsingularity.net Cc: Michal Hocko mhocko@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/mremap.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/mm/mremap.c +++ b/mm/mremap.c @@ -1016,7 +1016,8 @@ SYSCALL_DEFINE5(mremap, unsigned long, a long pages = (new_len - old_len) >> PAGE_SHIFT; unsigned long extension_start = addr + old_len; unsigned long extension_end = addr + new_len; - pgoff_t extension_pgoff = vma->vm_pgoff + (old_len >> PAGE_SHIFT); + pgoff_t extension_pgoff = vma->vm_pgoff + + ((extension_start - vma->vm_start) >> PAGE_SHIFT);
if (vma->vm_flags & VM_ACCOUNT) { if (security_vm_enough_memory_mm(mm, pages)) {