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arc=pass ("microsoft.com:s=arcselector9901:i=1") ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1663730284; a=rsa-sha256; cv=pass; b=RUnsti+Z2FgYyBsrP4APbh7g4pYHMFQb5AMpVJvrl4uJipFK44aMB+SWtWOmhoXOZXP0P8 s1VXOFf2+S3enAFq/r0oJ0TWv9eYhPebw4iSDv4uFLDUWCeDHidMaQ/CQeNztfu7HTQWO5 q9Wh2mFU/Je/FpYztaWOl6g5+qOw3Dw= Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2022-7-12 header.b=0E1uP1gH; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=y5lElzy2; dmarc=pass (policy=none) header.from=oracle.com; spf=pass (imf17.hostedemail.com: domain of mike.kravetz@oracle.com designates 205.220.177.32 as permitted sender) smtp.mailfrom=mike.kravetz@oracle.com; arc=pass ("microsoft.com:s=arcselector9901:i=1") X-Rspam-User: X-Rspamd-Server: rspam01 X-Stat-Signature: ahor8n9uxdb5nnq3ek6ds6m9zzf7prwt X-Rspamd-Queue-Id: 10FDD4001C X-HE-Tag: 1663730283-439070 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 09/21/22 01:48, HORIGUCHI NAOYA(堀口 直也) wrote: > On Fri, Sep 16, 2022 at 02:46:38PM -0700, Mike Kravetz wrote: > > v1 -> v2 > > - Fixed up head page in error path of __prep_compound_gigantic_page as > > discovered by Miaohe Lin. > > - Updated link to Matthew's Allocate and free frozen pages series. > > - Rebased on next-20220916 > > > > mm/hugetlb.c | 102 +++++++++++++++++++-------------------------------- > > 1 file changed, 38 insertions(+), 64 deletions(-) > > Hello Mike, > > I accidentally found a NULL pointer dereference when testing the latest > mm-unstable, which seems to be caused (or exposed?) by this patch > (I confirmed that it disappeared by reverting this patch). > > It's reproduced by doing like `sysctl vm.nr_hugepages=1000000` to allocate > hugepages as much as possible. > > Could you check that this patch is related to the issue? > > Thanks, > Naoya Horiguchi > > --- > [ 25.634476] BUG: kernel NULL pointer dereference, address: 0000000000000034 > [ 25.635980] #PF: supervisor write access in kernel mode > [ 25.637283] #PF: error_code(0x0002) - not-present page > [ 25.638365] PGD 0 P4D 0 > [ 25.638906] Oops: 0002 [#1] PREEMPT SMP PTI > [ 25.639779] CPU: 4 PID: 819 Comm: sysctl Tainted: G E N 6.0.0-rc3-v6.0-rc1-220920-1758-1398-g2b3f5+ #12 > [ 25.641928] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1.fc35 04/01/2014 > [ 25.643727] RIP: 0010:alloc_buddy_huge_page.isra.0+0x8c/0x140 > [ 25.645071] Code: fe ff 41 83 fc 01 0f 84 54 94 8b 00 41 bc 01 00 00 00 44 89 f7 4c 89 f9 44 89 ea 89 de e8 7c b9 fe ff 48 89 c7 b8 01 00 00 00 0f b1 6f 34 66 90 83 f8 01 75 c5 48 85 ff 74 52 65 48 ff 05 03 > [ 25.649006] RSP: 0018:ffffaa7181fffc18 EFLAGS: 00010286 > [ 25.650215] RAX: 0000000000000001 RBX: 0000000000000009 RCX: 0000000000000009 > [ 25.651672] RDX: ffffffffae3b6df0 RSI: ffffffffae8f7ce0 RDI: 0000000000000000 > [ 25.653115] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000c01 > [ 25.654579] R10: 0000000000000f90 R11: 0000000000000000 R12: 0000000000000002 > [ 25.656176] R13: 0000000000000000 R14: 0000000000346cca R15: ffffffffae8f7ce0 > [ 25.657637] FS: 00007f9252f2a740(0000) GS:ffff98cebbc00000(0000) knlGS:0000000000000000 > [ 25.659292] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 25.660469] CR2: 0000000000000034 CR3: 000000014924c004 CR4: 0000000000170ee0 > [ 25.661928] Call Trace: > [ 25.662469] > [ 25.662927] alloc_fresh_huge_page+0x16f/0x1d0 > [ 25.663859] alloc_pool_huge_page+0x6d/0xb0 > [ 25.664734] __nr_hugepages_store_common+0x189/0x3e0 > [ 25.665764] ? __do_proc_doulongvec_minmax+0x31f/0x340 > [ 25.666832] hugetlb_sysctl_handler_common+0xbf/0xd0 > [ 25.667861] ? hugetlb_register_node+0xe0/0xe0 > [ 25.668786] proc_sys_call_handler+0x196/0x2b0 > [ 25.669724] vfs_write+0x29b/0x3a0 > [ 25.670454] ksys_write+0x4f/0xd0 > [ 25.671153] do_syscall_64+0x3b/0x90 > [ 25.671909] entry_SYSCALL_64_after_hwframe+0x63/0xcd > [ 25.672958] RIP: 0033:0x7f9252d3e727 > [ 25.673712] Code: 0b 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24 > [ 25.677470] RSP: 002b:00007ffcdf9904a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 > [ 25.679002] RAX: ffffffffffffffda RBX: 000055c6ae683210 RCX: 00007f9252d3e727 > [ 25.680456] RDX: 0000000000000006 RSI: 000055c6ae683250 RDI: 0000000000000003 > [ 25.681910] RBP: 000055c6ae685380 R08: 0000000000000003 R09: 0000000000000077 > [ 25.683373] R10: 000000000000006b R11: 0000000000000246 R12: 0000000000000006 > [ 25.684824] R13: 0000000000000006 R14: 0000000000000006 R15: 00007f9252df59e0 > [ 25.686293] Hello Naoya, My bad for an obvious mistake! Note this change in the patch, > @@ -1951,7 +1953,21 @@ static struct page *alloc_buddy_huge_page(struct hstate *h, > gfp_mask |= __GFP_RETRY_MAYFAIL; > if (nid == NUMA_NO_NODE) > nid = numa_mem_id(); > +retry: > page = __alloc_pages(gfp_mask, order, nid, nmask); > + > + /* Freeze head page */ > + if (!page_ref_freeze(page, 1)) { > + __free_pages(page, order); > + if (retry) { /* retry once */ > + retry = false; > + goto retry; > + } > + /* WOW! twice in a row. */ > + pr_warn("HugeTLB head page unexpected inflated ref count\n"); > + page = NULL; > + } > + > if (page) > __count_vm_event(HTLB_BUDDY_PGALLOC); > else It does not check for a successful return from __alloc_pages before trying to freeze 'page'. It should obviously check for page == NULL before trying to freeze with something like this. diff --git a/mm/hugetlb.c b/mm/hugetlb.c index db90658db171..a092dd639687 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1961,7 +1961,7 @@ static struct page *alloc_buddy_huge_page(struct hstate *h, page = __alloc_pages(gfp_mask, order, nid, nmask); /* Freeze head page */ - if (!page_ref_freeze(page, 1)) { + if (page && !page_ref_freeze(page, 1)) { __free_pages(page, order); if (retry) { /* retry once */ retry = false; I will send out a v3 (my) tomorrow. -- Mike Kravetz