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While uprobe refuses hugetlb > early, make_device_exclusive_range() can end up getting called on > hugetlb VMAs. > > Right now, this means that with a PMD-sized hugetlb page, we can end > up calling split_huge_pmd(), because pmd_trans_huge() also succeeds > with hugetlb PMDs. > > For example, using a modified hmm-test selftest one can trigger: I haven't explicitly tested this with nouveau but I can't see anything that would prevent this being called on a hugetlb vma there either. Reviewed-by: Alistair Popple > [ 207.017134][T14945] ------------[ cut here ]------------ > [ 207.018614][T14945] kernel BUG at mm/page_table_check.c:87! > [ 207.019716][T14945] Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI > [ 207.021072][T14945] CPU: 3 UID: 0 PID: ... > [ 207.023036][T14945] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-2.fc40 04/01/2014 > [ 207.024834][T14945] RIP: 0010:page_table_check_clear.part.0+0x488/0x510 > [ 207.026128][T14945] Code: ... > [ 207.029965][T14945] RSP: 0018:ffffc9000cb8f348 EFLAGS: 00010293 > [ 207.031139][T14945] RAX: 0000000000000000 RBX: 00000000ffffffff RCX: ffffffff8249a0cd > [ 207.032649][T14945] RDX: ffff88811e883c80 RSI: ffffffff8249a357 RDI: ffff88811e883c80 > [ 207.034183][T14945] RBP: ffff888105c0a050 R08: 0000000000000005 R09: 0000000000000000 > [ 207.035688][T14945] R10: 00000000ffffffff R11: 0000000000000003 R12: 0000000000000001 > [ 207.037203][T14945] R13: 0000000000000200 R14: 0000000000000001 R15: dffffc0000000000 > [ 207.038711][T14945] FS: 00007f2783275740(0000) GS:ffff8881f4980000(0000) knlGS:0000000000000000 > [ 207.040407][T14945] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 207.041660][T14945] CR2: 00007f2782c00000 CR3: 0000000132356000 CR4: 0000000000750ef0 > [ 207.043196][T14945] PKRU: 55555554 > [ 207.043880][T14945] Call Trace: > [ 207.044506][T14945] > [ 207.045086][T14945] ? __die+0x51/0x92 > [ 207.045864][T14945] ? die+0x29/0x50 > [ 207.046596][T14945] ? do_trap+0x250/0x320 > [ 207.047430][T14945] ? do_error_trap+0xe7/0x220 > [ 207.048346][T14945] ? page_table_check_clear.part.0+0x488/0x510 > [ 207.049535][T14945] ? handle_invalid_op+0x34/0x40 > [ 207.050494][T14945] ? page_table_check_clear.part.0+0x488/0x510 > [ 207.051681][T14945] ? exc_invalid_op+0x2e/0x50 > [ 207.052589][T14945] ? asm_exc_invalid_op+0x1a/0x20 > [ 207.053596][T14945] ? page_table_check_clear.part.0+0x1fd/0x510 > [ 207.054790][T14945] ? page_table_check_clear.part.0+0x487/0x510 > [ 207.055993][T14945] ? page_table_check_clear.part.0+0x488/0x510 > [ 207.057195][T14945] ? page_table_check_clear.part.0+0x487/0x510 > [ 207.058384][T14945] __page_table_check_pmd_clear+0x34b/0x5a0 > [ 207.059524][T14945] ? __pfx___page_table_check_pmd_clear+0x10/0x10 > [ 207.060775][T14945] ? __pfx___mutex_unlock_slowpath+0x10/0x10 > [ 207.061940][T14945] ? __pfx___lock_acquire+0x10/0x10 > [ 207.062967][T14945] pmdp_huge_clear_flush+0x279/0x360 > [ 207.064024][T14945] split_huge_pmd_locked+0x82b/0x3750 > ... > > Before commit 9cb28da54643 ("mm/gup: handle hugetlb in the generic > follow_page_mask code"), we would have ignored the flag; instead, let's > simply refuse the combination completely in check_vma_flags(): the > caller is likely not prepared to handle any hugetlb folios. > > We'll teach make_device_exclusive_range() separately to ignore any hugetlb > folios as a future-proof safety net. > > Fixes: 9cb28da54643 ("mm/gup: handle hugetlb in the generic follow_page_mask code") > Cc: > Signed-off-by: David Hildenbrand > --- > mm/gup.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/gup.c b/mm/gup.c > index 3883b307780e..61e751baf862 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1283,6 +1283,9 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) > if ((gup_flags & FOLL_LONGTERM) && vma_is_fsdax(vma)) > return -EOPNOTSUPP; > > + if ((gup_flags & FOLL_SPLIT_PMD) && is_vm_hugetlb_page(vma)) > + return -EOPNOTSUPP; > + > if (vma_is_secretmem(vma)) > return -EFAULT; > > -- > 2.48.1 >