From: Oscar Salvador <osalvador@xxxxxxx> commit 8daf9c702ee7f825f0de8600abff764acfedea13 upstream. sysbot reported a splat [1] on __unmap_hugepage_range(). This is because vma_needs_reservation() can return -ENOMEM if allocate_file_region_entries() fails to allocate the file_region struct for the reservation. Check for that and do not call vma_add_reservation() if that is the case, otherwise region_abort() and region_del() will see that we do not have any file_regions. If we detect that vma_needs_reservation() returned -ENOMEM, we clear the hugetlb_restore_reserve flag as if this reservation was still consumed, so free_huge_folio() will not increment the resv count. [1] https://lore.kernel.org/linux-mm/0000000000004096100617c58d54@xxxxxxxxxx/T/#ma5983bc1ab18a54910da83416b3f89f3c7ee43aa Link: https://lkml.kernel.org/r/20240528205323.20439-1-osalvador@xxxxxxx Fixes: df7a6d1f6405 ("mm/hugetlb: restore the reservation if needed") Signed-off-by: Oscar Salvador <osalvador@xxxxxxx> Reported-and-tested-by: syzbot+d3fe2dc5ffe9380b714b@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://lore.kernel.org/linux-mm/0000000000004096100617c58d54@xxxxxxxxxx/ Cc: Breno Leitao <leitao@xxxxxxxxxx> Cc: Muchun Song <muchun.song@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/hugetlb.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5774,8 +5774,20 @@ void __unmap_hugepage_range(struct mmu_g * do_exit() will not see it, and will keep the reservation * forever. */ - if (adjust_reservation && vma_needs_reservation(h, vma, address)) - vma_add_reservation(h, vma, address); + if (adjust_reservation) { + int rc = vma_needs_reservation(h, vma, address); + + if (rc < 0) + /* Pressumably allocate_file_region_entries failed + * to allocate a file_region struct. Clear + * hugetlb_restore_reserve so that global reserve + * count will not be incremented by free_huge_folio. + * Act as if we consumed the reservation. + */ + folio_clear_hugetlb_restore_reserve(page_folio(page)); + else if (rc) + vma_add_reservation(h, vma, address); + } tlb_remove_page_size(tlb, page, huge_page_size(h)); /* Patches currently in stable-queue which might be from osalvador@xxxxxxx are queue-6.9/mm-hugetlb-do-not-call-vma_add_reservation-upon-enomem.patch
