From: Audra Mitchell <audra@redhat.com>
To: David Hildenbrand <david@redhat.com>
Cc: viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
akpm@linux-foundation.org, shuah@kernel.org,
linux-kselftest@vger.kernel.org, linux-mm@kvack.org,
raquini@redhat.com, Peter Xu <peterx@redhat.com>
Subject: Re: [PATCH 1/2] Fix userfaultfd_api to return EINVAL as expected
Date: Wed, 8 May 2024 08:58:42 -0400 [thread overview]
Message-ID: <Zjt3Apr8ILFA4oK_@fedora> (raw)
In-Reply-To: <939a16f2-7b66-45a6-a043-4821bd3c71dc@redhat.com>
On Wed, May 08, 2024 at 09:39:10AM +0200, David Hildenbrand wrote:
> On 07.05.24 21:55, Audra Mitchell wrote:
> > Currently if we request a feature that is not set in the Kernel
> > config we fail silently and return the available features. However, the
> > documentation indicates we should return an EINVAL.
>
> I assume you are referencing
>
> "EINVAL The API version requested in the api field is not supported by this
> kernel, or the features field passed to the kernel includes feature bits
> that are not supported by the current kernel version."
>
> and
>
> "To enable userfaultfd features the application should set a bit
> corresponding to each feature it wants to enable in the features field. If
> the kernel supports all the requested features it will enable them.
> Otherwise it will zero out the returned uffdio_api structure and return
> EINVAL.
> "
>
> in which case I agree.
Yep! I'm referencing the man page.
>
> >
> > We need to fix this issue since we can end up with a Kernel warning
> > should a program request the feature UFFD_FEATURE_WP_UNPOPULATED on
> > a kernel with the config not set with this feature.
>
> Can you mention which exact one? Is it a WARN* or a pr_warn() ?
Here is the kernel warning I get:
[ 200.803094] unrecognized swap entry 0x7c00000000000001
[ 200.808270] ------------[ cut here ]------------
[ 200.812896] WARNING: CPU: 91 PID: 13634 at mm/memory.c:1660 zap_pte_range+0x43d/0x660
[ 200.820738] Modules linked in: qrtr bridge stp llc rfkill sunrpc amd_atl intel_rapl_msr intel_rapl_common amd64_edac edac_mce_amd kvm_amd kvm ipmi_ssif acpi_ipmi i2c_piix4 ipmi_si wmi_bmof dcdbas dell_smbios dell_wmi_descriptor ptdma ipmi_devintf rapl ipmi_msghandler acpi_power_meter pcspkr k10temp xfs libcrc32c sd_mod t10_pi mgag200 sg drm_kms_helper crct10dif_pclmul i2c_algo_bit ahci crc32_pclmul drm_shmem_helper libahci crc32c_intel drm i40e libata ghash_clmulni_intel tg3 ccp megaraid_sas sp5100_tco wmi dm_mirror dm_region_hash dm_log dm_mod fuse
[ 200.869387] CPU: 91 PID: 13634 Comm: userfaultfd Kdump: loaded Not tainted 6.9.0-rc5+ #8
[ 200.877477] Hardware name: Dell Inc. PowerEdge R6525/0N7YGH, BIOS 2.7.3 03/30/2022
[ 200.885052] RIP: 0010:zap_pte_range+0x43d/0x660
[ 200.889595] Code: 83 fa 02 0f 86 44 01 00 00 83 f9 17 0f 84 e1 00 00 00 83 f9 1f 0f 84 d0 00 00 00 48 89 c6 48 c7 c7 00 e4 dd bb e8 73 a2 de ff <0f> 0b e9 44 fd ff ff 45 0f b6 44 24 20 41 f6 c0 f4 75 27 4c 89 ee
[ 200.908348] RSP: 0018:ffffa18d2e6c37c8 EFLAGS: 00010246
[ 200.913584] RAX: 000000000000002a RBX: 00007f26d3600000 RCX: 0000000000000000
[ 200.920730] RDX: 0000000000000000 RSI: ffff93503f9a0bc0 RDI: ffff93503f9a0bc0
[ 200.927867] RBP: 00007f26d35cc000 R08: 0000000000000000 R09: ffffa18d2e6c3688
[ 200.935009] R10: ffffa18d2e6c3680 R11: ffffffffbc9de448 R12: ffffa18d2e6c39e8
[ 200.942149] R13: ffff92d1ebc15b50 R14: ffff93114e0cde60 R15: ffffa18d2e6c3928
[ 200.949291] FS: 0000000000000000(0000) GS:ffff93503f980000(0000) knlGS:0000000000000000
[ 200.957384] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 200.963140] CR2: 00007f26b1600658 CR3: 00000040905ba000 CR4: 0000000000350ef0
[ 200.970283] Call Trace:
[ 200.972745] <TASK>
[ 200.974862] ? __warn+0x7f/0x130
[ 200.978108] ? zap_pte_range+0x43d/0x660
[ 200.982044] ? report_bug+0x18a/0x1a0
[ 200.985720] ? handle_bug+0x3c/0x70
[ 200.989219] ? exc_invalid_op+0x14/0x70
[ 200.993068] ? asm_exc_invalid_op+0x16/0x20
[ 200.997265] ? zap_pte_range+0x43d/0x660
[ 201.001199] ? zap_pte_range+0x43d/0x660
[ 201.005134] zap_pmd_range.isra.0+0xf9/0x230
[ 201.009416] unmap_page_range+0x2d4/0x4a0
[ 201.013436] unmap_vmas+0xa8/0x180
[ 201.016854] exit_mmap+0xea/0x3b0
[ 201.020191] __mmput+0x43/0x120
[ 201.023342] exit_mm+0xb1/0x110
[ 201.026496] do_exit+0x270/0x4f0
[ 201.029739] do_group_exit+0x2c/0x80
[ 201.033326] get_signal+0x886/0x8b0
[ 201.036828] ? srso_return_thunk+0x5/0x5f
[ 201.040848] arch_do_signal_or_restart+0x25/0x100
[ 201.045563] ? srso_return_thunk+0x5/0x5f
[ 201.049583] ? vma_set_page_prot+0x5e/0xc0
[ 201.053692] ? srso_return_thunk+0x5/0x5f
[ 201.057713] ? syscall_exit_work+0xff/0x130
[ 201.061908] syscall_exit_to_user_mode+0x1b3/0x200
[ 201.066712] do_syscall_64+0x87/0x160
[ 201.070387] ? srso_return_thunk+0x5/0x5f
[ 201.074405] ? do_mmap+0x416/0x5f0
[ 201.077821] ? srso_return_thunk+0x5/0x5f
[ 201.081840] ? rseq_get_rseq_cs+0x1d/0x240
[ 201.085950] ? srso_return_thunk+0x5/0x5f
[ 201.089970] ? rseq_ip_fixup+0x6d/0x1d0
[ 201.093823] ? vm_mmap_pgoff+0x117/0x1a0
[ 201.097755] ? srso_return_thunk+0x5/0x5f
[ 201.101776] ? srso_return_thunk+0x5/0x5f
[ 201.105795] ? syscall_exit_to_user_mode+0x78/0x200
[ 201.110685] ? srso_return_thunk+0x5/0x5f
[ 201.114706] ? do_syscall_64+0x87/0x160
[ 201.118557] ? srso_return_thunk+0x5/0x5f
[ 201.122575] ? __count_memcg_events+0x49/0xb0
[ 201.126944] ? srso_return_thunk+0x5/0x5f
[ 201.130967] ? srso_return_thunk+0x5/0x5f
[ 201.134986] ? syscall_exit_work+0xff/0x130
[ 201.139184] ? srso_return_thunk+0x5/0x5f
[ 201.143205] ? syscall_exit_to_user_mode+0x78/0x200
[ 201.148093] ? srso_return_thunk+0x5/0x5f
[ 201.152114] ? do_syscall_64+0x87/0x160
[ 201.155960] ? srso_return_thunk+0x5/0x5f
[ 201.159984] ? sched_clock_cpu+0xb/0x190
[ 201.163916] ? srso_return_thunk+0x5/0x5f
[ 201.167939] ? irqtime_account_irq+0x40/0xc0
[ 201.172220] ? srso_return_thunk+0x5/0x5f
[ 201.176243] ? srso_return_thunk+0x5/0x5f
[ 201.180263] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 201.185326] RIP: 0033:0x7f26dfd0735b
[ 201.188939] Code: Unable to access opcode bytes at 0x7f26dfd07331.
[ 201.195128] RSP: 002b:00007fffce176868 EFLAGS: 00000206 ORIG_RAX: 000000000000000a
[ 201.202700] RAX: fffffffffffffffc RBX: 00007f26dfe60000 RCX: 00007f26dfd0735b
[ 201.209841] RDX: 0000000000000003 RSI: 0000000001000000 RDI: 00007f26af401000
[ 201.216983] RBP: 00007f26b0400640 R08: 00000000ffffffff R09: 0000000000000000
[ 201.224127] R10: ffffffffffffffc0 R11: 0000000000000206 R12: 0000000000000000
[ 201.231267] R13: 000000000040d320 R14: 0000000000000000 R15: 0000000000000000
[ 201.238413] </TASK>
[ 201.240610] ---[ end trace 0000000000000000 ]---
[ 201.245250] unrecognized swap entry 0x7c00000000000001
>
> Likely we want "Fixes:" here.
This could be seen as a continuation of the problem
2ff559f31a5d Revert "userfaultfd: don't fail on unrecognized features"
was trying to solve. However, this patch only checks to make sure we didnt
ask for a feature outside the possible range of features. We are still missing
a check to confirm the requested features are also configured on. So I guess
the "Fixes" tag would be for this patch?
914eedcb9ba0 userfaultfd: don't fail on unrecognized features
Happy to get your input here!
Thanks in advance!
>
> >
> > Signed-off-by: Audra Mitchell <audra@redhat.com>
> > ---
> > fs/userfaultfd.c | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> > index 60dcfafdc11a..17210558de79 100644
> > --- a/fs/userfaultfd.c
> > +++ b/fs/userfaultfd.c
> > @@ -2073,6 +2073,11 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx,
> > uffdio_api.features &= ~UFFD_FEATURE_WP_UNPOPULATED;
> > uffdio_api.features &= ~UFFD_FEATURE_WP_ASYNC;
> > #endif
> > +
> > + ret = -EINVAL;
> > + if (features & ~uffdio_api.features)
> > + goto err_out;
> > +
> > uffdio_api.ioctls = UFFD_API_IOCTLS;
> > ret = -EFAULT;
> > if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
>
> CCing Peter.
>
> --
> Cheers,
>
> David / dhildenb
>
next prev parent reply other threads:[~2024-05-08 12:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-07 19:55 [PATCH 1/2] Fix userfaultfd_api to return EINVAL as expected Audra Mitchell
2024-05-07 19:55 ` [PATCH 2/2] Update uffd-stress to handle EINVAL for unset config features Audra Mitchell
2024-05-08 7:39 ` [PATCH 1/2] Fix userfaultfd_api to return EINVAL as expected David Hildenbrand
2024-05-08 12:58 ` Audra Mitchell [this message]
2024-05-08 14:11 ` Peter Xu
2024-05-08 16:43 ` David Hildenbrand
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