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[2003:cb:c734:b800:12c4:65cd:348a:aee6]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-439452533ecsm23523535e9.0.2025.02.10.11.38.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 10 Feb 2025 11:38:07 -0800 (PST) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-doc@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-mm@kvack.org, nouveau@lists.freedesktop.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, damon@lists.linux.dev, David Hildenbrand , Andrew Morton , =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= , Jonathan Corbet , Alex Shi , Yanteng Si , Karol Herbst , Lyude Paul , Danilo Krummrich , David Airlie , Simona Vetter , Masami Hiramatsu , Oleg Nesterov , Peter Zijlstra , SeongJae Park , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pasha Tatashin , Peter Xu , Alistair Popple , Jason Gunthorpe , John Hubbard , stable@vger.kernel.org Subject: [PATCH v2 01/17] mm/gup: reject FOLL_SPLIT_PMD with hugetlb VMAs Date: Mon, 10 Feb 2025 20:37:43 +0100 Message-ID: <20250210193801.781278-2-david@redhat.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250210193801.781278-1-david@redhat.com> References: <20250210193801.781278-1-david@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" We only have two FOLL_SPLIT_PMD users. 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: [ 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 NO= PTI [ 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: fff= fffff8249a0cd [ 207.032649][T14945] RDX: ffff88811e883c80 RSI: ffffffff8249a357 RDI: fff= f88811e883c80 [ 207.034183][T14945] RBP: ffff888105c0a050 R08: 0000000000000005 R09: 000= 0000000000000 [ 207.035688][T14945] R10: 00000000ffffffff R11: 0000000000000003 R12: 000= 0000000000001 [ 207.037203][T14945] R13: 0000000000000200 R14: 0000000000000001 R15: dff= ffc0000000000 [ 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: 000= 0000000750ef0 [ 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_mas= k code") Reviewed-by: John Hubbard Reviewed-by: Alistair Popple 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 3883b307780ea..61e751baf862c 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; =20 + if ((gup_flags & FOLL_SPLIT_PMD) && is_vm_hugetlb_page(vma)) + return -EOPNOTSUPP; + if (vma_is_secretmem(vma)) return -EFAULT; =20 --=20 2.48.1