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drm/shmem-helper: Fix huge page mapping in fault handler
When running ./tools/testing/selftests/mm/split_huge_page_test multiple
times with /sys/kernel/mm/transparent_hugepage/shmem_enabled and
/sys/kernel/mm/transparent_hugepage/enabled set as always the following BUG
occurs:
[ 232.728858] ------------[ cut here ]------------
[ 232.729458] kernel BUG at mm/memory.c:2276!
[ 232.729726] Oops: invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
[ 232.730217] CPU: 19 UID: 60578 PID: 1497 Comm: llvmpipe-9 Not tainted 7.0.0-rc1mm-new+ #19 PREEMPT(lazy)
[ 232.730855] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-9.fc43 06/10/2025
[ 232.731360] RIP: 0010:walk_to_pmd+0x29e/0x3c0
[ 232.731569] Code: d8 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc 48 89 ea 48 89 de 4c 89 f7 e8 ae 85 ff ff 85 c0 0f 84 1f fe ff ff 31 db eb d0 <0f> 0b 48 89 ea 48 89 de 4c 89 f7 e8 92 8b ff ff 85 c0 75 e8 48 b8
[ 232.732614] RSP: 0000:ffff8881aa6ff9a8 EFLAGS: 00010282
[ 232.732991] RAX: 8000000142e002e7 RBX: ffff8881433cae10 RCX: dffffc0000000000
[ 232.733362] RDX: 0000000000000000 RSI: 00007fb47840b000 RDI: 8000000142e002e7
[ 232.733801] RBP: 00007fb47840b000 R08: 0000000000000000 R09: 1ffff110354dff46
[ 232.734168] R10: fffffbfff0cb921d R11: 00000000910da5ce R12: 1ffffffff0c1fcdd
[ 232.734459] R13: 1ffffffff0c23f36 R14: ffff888171628040 R15: 0000000000000000
[ 232.734861] FS: 00007fb4907f86c0(0000) GS:ffff888791f2c000(0000) knlGS:0000000000000000
[ 232.735265] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 232.735548] CR2: 00007fb47840be00 CR3: 000000015e6dc000 CR4: 00000000000006f0
[ 232.736031] Call Trace:
[ 232.736273] <TASK>
[ 232.736500] get_locked_pte+0x1f/0xa0
[ 232.736878] insert_pfn+0x9f/0x350
[ 232.737190] ? __pfx_pat_pagerange_is_ram+0x10/0x10
[ 232.737614] ? __pfx_insert_pfn+0x10/0x10
[ 232.737990] ? __pfx_css_rstat_updated+0x10/0x10
[ 232.738281] ? __pfx_pfn_modify_allowed+0x10/0x10
[ 232.738552] ? lookup_memtype+0x62/0x180
[ 232.738761] vmf_insert_pfn_prot+0x14b/0x340
[ 232.739012] ? __pfx_vmf_insert_pfn_prot+0x10/0x10
[ 232.739247] ? __pfx___might_resched+0x10/0x10
[ 232.739475] drm_gem_shmem_fault.cold+0x18/0x39
[ 232.739677] ? rcu_read_unlock+0x20/0x70
[ 232.739882] __do_fault+0x251/0x7b0
[ 232.740028] do_fault+0x6e1/0xc00
[ 232.740167] ? __lock_acquire+0x590/0xc40
[ 232.740335] handle_pte_fault+0x439/0x760
[ 232.740498] ? mtree_range_walk+0x252/0xae0
[ 232.740669] ? __pfx_handle_pte_fault+0x10/0x10
[ 232.740899] __handle_mm_fault+0xa02/0xf30
[ 232.741066] ? __pfx___handle_mm_fault+0x10/0x10
[ 232.741255] ? find_vma+0xa1/0x120
[ 232.741403] handle_mm_fault+0x2bf/0x8f0
[ 232.741564] do_user_addr_fault+0x2d3/0xed0
[ 232.741736] ? trace_page_fault_user+0x1bf/0x240
[ 232.741969] exc_page_fault+0x87/0x120
[ 232.742124] asm_exc_page_fault+0x26/0x30
[ 232.742288] RIP: 0033:0x7fb4d73ed546
[ 232.742441] Code: 66 41 0f 6f fb 66 44 0f 6d dc 66 44 0f 6f c6 66 41 0f 6d f1 66 0f 6c fc 66 45 0f 6c c1 66 44 0f 6f c9 66 0f 6d ca 66 0f db f0 <66> 0f df 04 08 66 44 0f 6c ca 66 45 0f db c2 66 44 0f df 10 66 44
[ 232.743193] RSP: 002b:00007fb4907f68a0 EFLAGS: 00010206
[ 232.743565] RAX: 00007fb47840aa00 RBX: 00007fb4d73ec070 RCX: 0000000000001400
[ 232.743871] RDX: 0000000000002800 RSI: 0000000000003c00 RDI: 0000000000000001
[ 232.744150] RBP: 0000000000000004 R08: 0000000000001400 R09: 00007fb4d73ec060
[ 232.744433] R10: 000055f0261a4288 R11: 00007fb4c013da40 R12: 0000000000000008
[ 232.744712] R13: 0000000000000000 R14: 4332322132212110 R15: 0000000000000004
[ 232.746616] </TASK>
[ 232.746711] Modules linked in: nft_nat nft_masq veth bridge stp llc snd_seq_dummy snd_hrtimer snd_seq snd_seq_device snd_timer snd soundcore overlay rfkill nf_conntrack_netbios_ns nf_conntrack_broadcast nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nf_tables qrtr ppdev 9pnet_virtio 9pnet parport_pc i2c_piix4 netfs pcspkr parport i2c_smbus joydev sunrpc vfat fat loop dm_multipath nfnetlink vsock_loopback vmw_vsock_virtio_transport_common vmw_vsock_vmci_transport zram lz4hc_compress vmw_vmci lz4_compress vsock e1000 bochs serio_raw ata_generic pata_acpi scsi_dh_rdac scsi_dh_emc scsi_dh_alua i2c_dev fuse qemu_fw_cfg
[ 232.749308] ---[ end trace 0000000000000000 ]---
[ 232.749507] RIP: 0010:walk_to_pmd+0x29e/0x3c0
[ 232.749692] Code: d8 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc 48 89 ea 48 89 de 4c 89 f7 e8 ae 85 ff ff 85 c0 0f 84 1f fe ff ff 31 db eb d0 <0f> 0b 48 89 ea 48 89 de 4c 89 f7 e8 92 8b ff ff 85 c0 75 e8 48 b8
[ 232.750428] RSP: 0000:ffff8881aa6ff9a8 EFLAGS: 00010282
[ 232.750645] RAX: 8000000142e002e7 RBX: ffff8881433cae10 RCX: dffffc0000000000
[ 232.750954] RDX: 0000000000000000 RSI: 00007fb47840b000 RDI: 8000000142e002e7
[ 232.751232] RBP: 00007fb47840b000 R08: 0000000000000000 R09: 1ffff110354dff46
[ 232.751514] R10: fffffbfff0cb921d R11: 00000000910da5ce R12: 1ffffffff0c1fcdd
[ 232.751837] R13: 1ffffffff0c23f36 R14: ffff888171628040 R15: 0000000000000000
[ 232.752124] FS: 00007fb4907f86c0(0000) GS:ffff888791f2c000(0000) knlGS:0000000000000000
[ 232.752441] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 232.752674] CR2: 00007fb47840be00 CR3: 000000015e6dc000 CR4: 00000000000006f0
[ 232.752983] Kernel panic - not syncing: Fatal exception
[ 232.753510] Kernel Offset: disabled
[ 232.754643] ---[ end Kernel panic - not syncing: Fatal exception ]---
This happens when two concurrent page faults occur within the same PMD range.
One fault installs a PMD mapping through vmf_insert_pfn_pmd(), while the other
attempts to install a PTE mapping via vmf_insert_pfn(). The bug is
triggered because a pmd_trans_huge is not expected when walking the page
table inside vmf_insert_pfn.
Avoid this race by adding a huge_fault callback to drm_gem_shmem_vm_ops so that
PMD-sized mappings are handled through the appropriate huge page fault path.
Fixes: 211b9a39f2 ("drm/shmem-helper: Map huge pages in fault handler")
Signed-off-by: Pedro Demarchi Gomes <pedrodemargomes@gmail.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patch.msgid.link/20260319015224.46896-1-pedrodemargomes@gmail.com
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
This commit is contained in:
Pedro Demarchi Gomes
committed by
Boris Brezillon
Boris Brezillon
parent
cffcb42c57
commit
fc3bbf34e6
@@ -550,27 +550,27 @@ int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
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}
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EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create);
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static bool drm_gem_shmem_try_map_pmd(struct vm_fault *vmf, unsigned long addr,
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struct page *page)
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static vm_fault_t try_insert_pfn(struct vm_fault *vmf, unsigned int order,
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unsigned long pfn)
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{
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if (!order) {
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return vmf_insert_pfn(vmf->vma, vmf->address, pfn);
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#ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP
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unsigned long pfn = page_to_pfn(page);
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unsigned long paddr = pfn << PAGE_SHIFT;
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bool aligned = (addr & ~PMD_MASK) == (paddr & ~PMD_MASK);
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} else if (order == PMD_ORDER) {
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unsigned long paddr = pfn << PAGE_SHIFT;
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bool aligned = (vmf->address & ~PMD_MASK) == (paddr & ~PMD_MASK);
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if (aligned &&
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pmd_none(*vmf->pmd) &&
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folio_test_pmd_mappable(page_folio(page))) {
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pfn &= PMD_MASK >> PAGE_SHIFT;
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if (vmf_insert_pfn_pmd(vmf, pfn, false) == VM_FAULT_NOPAGE)
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return true;
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}
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if (aligned &&
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folio_test_pmd_mappable(page_folio(pfn_to_page(pfn)))) {
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pfn &= PMD_MASK >> PAGE_SHIFT;
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return vmf_insert_pfn_pmd(vmf, pfn, false);
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}
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#endif
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return false;
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}
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return VM_FAULT_FALLBACK;
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}
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static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
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static vm_fault_t drm_gem_shmem_any_fault(struct vm_fault *vmf, unsigned int order)
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{
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struct vm_area_struct *vma = vmf->vma;
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struct drm_gem_object *obj = vma->vm_private_data;
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@@ -581,6 +581,9 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
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pgoff_t page_offset;
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unsigned long pfn;
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if (order && order != PMD_ORDER)
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return VM_FAULT_FALLBACK;
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/* Offset to faulty address in the VMA. */
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page_offset = vmf->pgoff - vma->vm_pgoff;
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@@ -593,13 +596,8 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
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goto out;
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}
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if (drm_gem_shmem_try_map_pmd(vmf, vmf->address, pages[page_offset])) {
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ret = VM_FAULT_NOPAGE;
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goto out;
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}
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pfn = page_to_pfn(pages[page_offset]);
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ret = vmf_insert_pfn(vma, vmf->address, pfn);
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ret = try_insert_pfn(vmf, order, pfn);
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out:
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dma_resv_unlock(shmem->base.resv);
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@@ -607,6 +605,11 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
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return ret;
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}
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static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
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{
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return drm_gem_shmem_any_fault(vmf, 0);
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}
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static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
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{
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struct drm_gem_object *obj = vma->vm_private_data;
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@@ -643,6 +646,9 @@ static void drm_gem_shmem_vm_close(struct vm_area_struct *vma)
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const struct vm_operations_struct drm_gem_shmem_vm_ops = {
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.fault = drm_gem_shmem_fault,
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#ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP
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.huge_fault = drm_gem_shmem_any_fault,
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#endif
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.open = drm_gem_shmem_vm_open,
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.close = drm_gem_shmem_vm_close,
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};
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