On 17.08.21 16:01, David Hildenbrand wrote:
On 17.08.21 15:58, Mike Rapoport wrote:
From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Jiri Olsa reported a fault when running:
# cat /proc/kallsyms | grep ksys_read
ffffffff8136d580 T ksys_read
# objdump -d --start-address=0xffffffff8136d580 --stop-address=0xffffffff8136d590 /proc/kcore
/proc/kcore: file format elf64-x86-64
Segmentation fault
krava33 login: [ 68.330612] general protection fault, probably for non-canonical address 0xf887ffcbff000: 0000 [#1] SMP PTI
[ 68.333118] CPU: 12 PID: 1079 Comm: objdump Not tainted 5.14.0-rc5qemu+ #508
[ 68.334922] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-4.fc34 04/01/2014
[ 68.336945] RIP: 0010:kern_addr_valid+0x150/0x300
[ 68.338082] Code: 1f 40 00 48 8b 0d e8 12 61 01 48 85 f6 0f 85 ca 00 00 00 48 81 e1 00 f0 ff ff 48 21 c1 48 b8 00 00 00 00 80 88 ff ff 48 01 ca <48> 8b 3c 02 48 f7 c7 9f ff ff ff 0f 84 d8 fe ff ff 48 89 f8 0f 1f
[ 68.342220] RSP: 0018:ffffc90000bcbc38 EFLAGS: 00010206
[ 68.343428] RAX: ffff888000000000 RBX: 0000000000001000 RCX: 000ffffffcbff000
[ 68.345029] RDX: 000ffffffcbff000 RSI: 0000000000000000 RDI: 800ffffffcbff062
[ 68.346599] RBP: ffffc90000bcbea8 R08: 0000000000001000 R09: 0000000000000000
[ 68.349000] R10: 0000000000000000 R11: 0000000000001000 R12: 00007fcc0fd80010
[ 68.350804] R13: ffffffff83400000 R14: 0000000000400000 R15: ffffffff843d23e0
[ 68.352609] FS: 00007fcc111fcc80(0000) GS:ffff888275e00000(0000) knlGS:0000000000000000
[ 68.354638] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 68.356104] CR2: 00007fcc0fd80000 CR3: 000000011226e004 CR4: 0000000000770ee0
[ 68.357896] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 68.359694] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 68.361597] PKRU: 55555554
[ 68.362460] Call Trace:
[ 68.363252] read_kcore+0x57f/0x920
[ 68.364289] ? rcu_read_lock_sched_held+0x12/0x80
[ 68.365630] ? rcu_read_lock_sched_held+0x12/0x80
[ 68.366955] ? rcu_read_lock_sched_held+0x12/0x80
[ 68.368277] ? trace_hardirqs_on+0x1b/0xd0
[ 68.369462] ? rcu_read_lock_sched_held+0x12/0x80
[ 68.370793] ? lock_acquire+0x195/0x2f0
[ 68.371920] ? lock_acquire+0x195/0x2f0
[ 68.373035] ? rcu_read_lock_sched_held+0x12/0x80
[ 68.374364] ? lock_acquire+0x195/0x2f0
[ 68.375498] ? rcu_read_lock_sched_held+0x12/0x80
[ 68.376831] ? rcu_read_lock_sched_held+0x12/0x80
[ 68.379883] ? rcu_read_lock_sched_held+0x12/0x80
[ 68.381268] ? lock_release+0x22b/0x3e0
[ 68.382458] ? _raw_spin_unlock+0x1f/0x30
[ 68.383685] ? __handle_mm_fault+0xcfc/0x15f0
[ 68.384994] ? rcu_read_lock_sched_held+0x12/0x80
[ 68.386389] ? lock_acquire+0x195/0x2f0
[ 68.387573] ? rcu_read_lock_sched_held+0x12/0x80
[ 68.388969] ? lock_release+0x22b/0x3e0
[ 68.390145] proc_reg_read+0x55/0xa0
[ 68.391257] ? vfs_read+0x78/0x1b0
[ 68.392336] vfs_read+0xa7/0x1b0
[ 68.393328] ksys_read+0x68/0xe0
[ 68.394308] do_syscall_64+0x3b/0x90
[ 68.395391] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 68.396804] RIP: 0033:0x7fcc11cf92e2
[ 68.397824] Code: c0 e9 b2 fe ff ff 50 48 8d 3d ea 2e 0a 00 e8 95 e9 01 00 0f 1f 44 00 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 0f 05 <48> 3d 00 f0 ff ff 77 56 c3 0f 1f 44 00 00 48 83 ec 28 48 89 54 24
[ 68.402420] RSP: 002b:00007ffd6e0f8da8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[ 68.404357] RAX: ffffffffffffffda RBX: 0000565439305b20 RCX: 00007fcc11cf92e2
[ 68.406061] RDX: 0000000000800000 RSI: 00007fcc0f980010 RDI: 0000000000000003
[ 68.407747] RBP: 00007fcc11dcd300 R08: 0000000000000003 R09: 00007fcc0d980010
[ 68.410937] R10: 0000000003826000 R11: 0000000000000246 R12: 00007fcc0f980010
[ 68.412624] R13: 0000000000000d68 R14: 00007fcc11dcc700 R15: 0000000000800000
[ 68.414322] Modules linked in: intel_rapl_msr intel_rapl_common nfit kvm_intel kvm irqbypass rapl iTCO_wdt iTCO_vendor_support i2c_i801 i2c_smbus lpc_ich drm drm_panel_orientation_quirks zram xfs crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel
[ 68.419591] ---[ end trace e2c30f827226966b ]---
[ 68.420969] RIP: 0010:kern_addr_valid+0x150/0x300
[ 68.422308] Code: 1f 40 00 48 8b 0d e8 12 61 01 48 85 f6 0f 85 ca 00 00 00 48 81 e1 00 f0 ff ff 48 21 c1 48 b8 00 00 00 00 80 88 ff ff 48 01 ca <48> 8b 3c 02 48 f7 c7 9f ff ff ff 0f 84 d8 fe ff ff 48 89 f8 0f 1f
[ 68.426826] RSP: 0018:ffffc90000bcbc38 EFLAGS: 00010206
[ 68.428150] RAX: ffff888000000000 RBX: 0000000000001000 RCX: 000ffffffcbff000
[ 68.429813] RDX: 000ffffffcbff000 RSI: 0000000000000000 RDI: 800ffffffcbff062
[ 68.431465] RBP: ffffc90000bcbea8 R08: 0000000000001000 R09: 0000000000000000
[ 68.433115] R10: 0000000000000000 R11: 0000000000001000 R12: 00007fcc0fd80010
[ 68.434768] R13: ffffffff83400000 R14: 0000000000400000 R15: ffffffff843d23e0
[ 68.436423] FS: 00007fcc111fcc80(0000) GS:ffff888275e00000(0000) knlGS:0000000000000000
[ 68.438354] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 68.442077] CR2: 00007fcc0fd80000 CR3: 000000011226e004 CR4: 0000000000770ee0
[ 68.443727] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 68.445370] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 68.447010] PKRU: 55555554
The fault happens because kern_addr_valid() dereferences existent but not
present PMD in the high kernel mappings.
Such PMDs are created when free_kernel_image_pages() frees regions larger
than 2Mb. In this case a part of the freed memory is mapped with PMDs and
the set_memory_np_noalias() -> ... -> __change_page_attr() sequence will
mark the PMD as not present rather than wipe it completely.
Make kern_addr_valid() to check whether higher level page table entries are
present before trying to dereference them to fix this issue and to avoid
similar issues in the future.
Why not fix the setting code?
Reported-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
---
arch/x86/mm/init_64.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index ddeaba947eb3..07b56e90db5d 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1433,18 +1433,18 @@ int kern_addr_valid(unsigned long addr)
return 0;
p4d = p4d_offset(pgd, addr);
- if (p4d_none(*p4d))
+ if (p4d_none(*p4d) || !p4d_present(*p4d))
return 0;
if (!p4d_present(*p4d))
return 0;
should be sufficient I think.
Same applies to the others.
Oh, and I forgot, can we come up with Fixes: and Cc: stable tags?
--
Thanks,
David / dhildenb
