Re: [PATCH 6.3 00/13] 6.3.12-rc1 review

[Arnd Bergmann]

On Tue, Jul 4, 2023, at 09:34, Naresh Kamboju wrote:
> On Tue, 4 Jul 2023 at 00:26, Greg Kroah-Hartman
> [   54.386939] hugefallocate01 (410): drop_caches: 3
> g tests.......
> tst_hugepage.c:83: TINFO: 2 huge[   54.396708] BUG: kernel NULL
> pointer dereference, address: 0000000000000034
> [   54.404495] #PF: supervisor write access in kernel mode
> [   54.409718] #PF: error_code(0x0002) - not-present page
> [   54.414849] PGD 800000010394a067 P4D 800000010394a067 PUD 1033ba067 PMD 0
> [   54.421721] Oops: 0002 [#1] PREEMPT SMP PTI
> [   54.425900] CPU: 3 PID: 411 Comm: hugefallocate01 Not tainted 6.3.12-rc1 #1
> [   54.432860] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS
> 2.5 11/26/2020
> [   54.440244] RIP: 0010:hugetlbfs_fallocate+0x256/0x580
> [   54.445296] Code: 3d 6f 37 06 02 89 c3 48 c1 e3 05 48 01 df e8 71
> fa cb 00 31 c9 31 d2 4c 89 e6 4c 89 f7 e8 72 a6 de ff 48 3d 00 f0 ff
> ff 77 53 <f0> ff 48 34 74 43 48 03 1d 3d 37 06 02 48 89 df e8 25 f0 cb
> 00 48
> [   54.464041] RSP: 0018:ffffab24409f7dc0 EFLAGS: 00010207
> [   54.469260] RAX: 0000000000000000 RBX: 0000000000000080 RCX: 0000000000000000
> [   54.476390] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff9fe006b253c0
> [   54.483514] RBP: ffffab24409f7ec0 R08: 0000000000000000 R09: 0000000000000000
> [   54.490640] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
> [   54.497762] R13: ffff9fe006a68010 R14: ffff9fe006a68188 R15: 0000000000000000
> [   54.504887] FS:  00007f8bec2ff740(0000) GS:ffff9fe367b80000(0000)
> knlGS:0000000000000000
> [   54.512965] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   54.518702] CR2: 0000000000000034 CR3: 0000000101cd2003 CR4: 00000000003706e0
> [   54.525826] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [   54.532950] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [   54.540075] Call Trace:
> [   54.542519]  <TASK>
> [   54.544618]  ? show_regs+0x6e/0x80
> [   54.548022]  ? __die+0x29/0x70
> [   54.551080]  ? page_fault_oops+0x154/0x470
> [   54.555186]  ? do_user_addr_fault+0x2f3/0x580
> [   54.559551]  ? exc_page_fault+0x6b/0x170
> [   54.563502]  ? asm_exc_page_fault+0x2b/0x30
> [   54.567686]  ? hugetlbfs_fallocate+0x256/0x580

>From your vmlinux file I see this hugetlbfs_fallocate+0x256/0x580
is folio_put(NULL):

ffffffff815bdd29:       e8 72 a6 de ff          call   ffffffff813a83a0 <__filemap_get_folio>
ffffffff815bdd2e:       48 3d 00 f0 ff ff       cmp    $0xfffffffffffff000,%rax
ffffffff815bdd34:       77 53                   ja     ffffffff815bdd89 <hugetlbfs_fallocate+0x2a9>
ffffffff815bdd36:       f0 ff 48 34             lock decl 0x34(%rax)


                /* See if already present in mapping to avoid alloc/free */
                folio = filemap_get_folio(mapping, index);
                if (!IS_ERR(folio)) {
                        folio_put(folio);

It looks like filemap_get_folio() has always returned NULL on error
rather than an error pointer.

     Arnd