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: 211b9a39f261 ("drm/shmem-helper: Map huge pages in fault handler")
Signed-off-by: Pedro Demarchi Gomes <[email protected]>
---
drivers/gpu/drm/drm_gem_shmem_helper.c | 59 +++++++++++++++++++-------
1 file changed, 43 insertions(+), 16 deletions(-)
diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c
b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 7b5a49935ae4..4cd9080c598b 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -550,24 +550,53 @@ int drm_gem_shmem_dumb_create(struct drm_file *file,
struct drm_device *dev,
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create);
-static bool drm_gem_shmem_try_map_pmd(struct vm_fault *vmf, unsigned long addr,
- struct page *page)
+
+static vm_fault_t drm_gem_shmem_huge_fault(struct vm_fault *vmf,
+ unsigned int order)
{
-#ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP
- unsigned long pfn = page_to_pfn(page);
- unsigned long paddr = pfn << PAGE_SHIFT;
- bool aligned = (addr & ~PMD_MASK) == (paddr & ~PMD_MASK);
+ struct vm_area_struct *vma = vmf->vma;
+ struct drm_gem_object *obj = vma->vm_private_data;
+ struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
+ loff_t num_pages = obj->size >> PAGE_SHIFT;
+ vm_fault_t ret = VM_FAULT_FALLBACK;
+ struct page **pages = shmem->pages;
+ pgoff_t page_offset;
+ unsigned long pfn;
+ unsigned long paddr;
+ bool aligned;
+ struct page *page;
+
+ if (order != PMD_ORDER)
+ goto out_unlocked;
+
+ /* Offset to faulty address in the VMA. */
+ page_offset = vmf->pgoff - vma->vm_pgoff;
+
+ dma_resv_lock(shmem->base.resv, NULL);
+
+ if (page_offset >= num_pages ||
+ drm_WARN_ON_ONCE(obj->dev, !shmem->pages) ||
+ shmem->madv < 0) {
+ ret = VM_FAULT_SIGBUS;
+ goto out;
+ }
+
+ page = pages[page_offset];
+ pfn = page_to_pfn(page);
+ paddr = pfn << PAGE_SHIFT;
+ aligned = (vmf->address & ~PMD_MASK) == (paddr & ~PMD_MASK);
if (aligned &&
- pmd_none(*vmf->pmd) &&
folio_test_pmd_mappable(page_folio(page))) {
pfn &= PMD_MASK >> PAGE_SHIFT;
- if (vmf_insert_pfn_pmd(vmf, pfn, false) == VM_FAULT_NOPAGE)
- return true;
+ ret = vmf_insert_pfn_pmd(vmf, pfn, false);
}
-#endif
- return false;
+ out:
+ dma_resv_unlock(shmem->base.resv);
+
+ out_unlocked:
+ return ret;
}
static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
@@ -593,11 +622,6 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
goto out;
}
- if (drm_gem_shmem_try_map_pmd(vmf, vmf->address, pages[page_offset])) {
- ret = VM_FAULT_NOPAGE;
- goto out;
- }
-
pfn = page_to_pfn(pages[page_offset]);
ret = vmf_insert_pfn(vma, vmf->address, pfn);
@@ -643,6 +667,9 @@ static void drm_gem_shmem_vm_close(struct vm_area_struct
*vma)
const struct vm_operations_struct drm_gem_shmem_vm_ops = {
.fault = drm_gem_shmem_fault,
+ #ifdef CONFIG_ARCH_SUPPORTS_HUGE_PFNMAP
+ .huge_fault = drm_gem_shmem_huge_fault,
+ #endif
.open = drm_gem_shmem_vm_open,
.close = drm_gem_shmem_vm_close,
};
--
2.53.0
