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@xxxxxxxxxx> > > --- > > 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 >
