The return thunk call makes the fastop functions larger, just like IBT
does. Consider a 16-byte FASTOP_SIZE when CONFIG_RETHUNK is enabled.
Otherwise, functions will be incorrectly aligned and when computing their
position for differently sized operators, they will executed in the middle
or end of a function, which may as well be an int3, leading to a crash
like:
[ 36.091116] int3: 0000 [#1] SMP NOPTI
[ 36.091119] CPU: 3 PID: 1371 Comm: qemu-system-x86 Not tainted 5.15.0-41-generic #44
[ 36.091120] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014
[ 36.091121] RIP: 0010:xaddw_ax_dx+0x9/0x10 [kvm]
[ 36.091185] Code: 00 0f bb d0 c3 cc cc cc cc 48 0f bb d0 c3 cc cc cc cc 0f 1f 80 00 00 00 00 0f c0 d0 c3 cc cc cc cc 66 0f c1 d0 c3 cc cc cc cc <0f> 1f 80 00 00 00 00 0f c1 d0 c3 cc cc cc cc 48 0f c1 d0 c3 cc cc
[ 36.091186] RSP: 0018:
ffffb1f541143c98 EFLAGS:
00000202
[ 36.091188] RAX:
0000000089abcdef RBX:
0000000000000001 RCX:
0000000000000000
[ 36.091188] RDX:
0000000076543210 RSI:
ffffffffc073c6d0 RDI:
0000000000000200
[ 36.091189] RBP:
ffffb1f541143ca0 R08:
ffff9f1803350a70 R09:
0000000000000002
[ 36.091190] R10:
ffff9f1803350a70 R11:
0000000000000000 R12:
ffff9f1803350a70
[ 36.091190] R13:
ffffffffc077fee0 R14:
0000000000000000 R15:
0000000000000000
[ 36.091191] FS:
00007efdfce8d640(0000) GS:
ffff9f187dd80000(0000) knlGS:
0000000000000000
[ 36.091192] CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
[ 36.091192] CR2:
0000000000000000 CR3:
0000000009b62002 CR4:
0000000000772ee0
[ 36.091195] PKRU:
55555554
[ 36.091195] Call Trace:
[ 36.091197] <TASK>
[ 36.091198] ? fastop+0x5a/0xa0 [kvm]
[ 36.091222] x86_emulate_insn+0x7b8/0xe90 [kvm]
[ 36.091244] x86_emulate_instruction+0x2f4/0x630 [kvm]
[ 36.091263] ? kvm_arch_vcpu_load+0x7c/0x230 [kvm]
[ 36.091283] ? vmx_prepare_switch_to_host+0xf7/0x190 [kvm_intel]
[ 36.091290] complete_emulated_mmio+0x297/0x320 [kvm]
[ 36.091310] kvm_arch_vcpu_ioctl_run+0x32f/0x550 [kvm]
[ 36.091330] kvm_vcpu_ioctl+0x29e/0x6d0 [kvm]
[ 36.091344] ? kvm_vcpu_ioctl+0x120/0x6d0 [kvm]
[ 36.091357] ? __fget_files+0x86/0xc0
[ 36.091362] ? __fget_files+0x86/0xc0
[ 36.091363] __x64_sys_ioctl+0x92/0xd0
[ 36.091366] do_syscall_64+0x59/0xc0
[ 36.091369] ? syscall_exit_to_user_mode+0x27/0x50
[ 36.091370] ? do_syscall_64+0x69/0xc0
[ 36.091371] ? syscall_exit_to_user_mode+0x27/0x50
[ 36.091372] ? __x64_sys_writev+0x1c/0x30
[ 36.091374] ? do_syscall_64+0x69/0xc0
[ 36.091374] ? exit_to_user_mode_prepare+0x37/0xb0
[ 36.091378] ? syscall_exit_to_user_mode+0x27/0x50
[ 36.091379] ? do_syscall_64+0x69/0xc0
[ 36.091379] ? do_syscall_64+0x69/0xc0
[ 36.091380] ? do_syscall_64+0x69/0xc0
[ 36.091381] ? do_syscall_64+0x69/0xc0
[ 36.091381] entry_SYSCALL_64_after_hwframe+0x61/0xcb
[ 36.091384] RIP: 0033:0x7efdfe6d1aff
[ 36.091390] Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <41> 89 c0 3d 00 f0 ff ff 77 1f 48 8b 44 24 18 64 48 2b 04 25 28 00
[ 36.091391] RSP: 002b:
00007efdfce8c460 EFLAGS:
00000246 ORIG_RAX:
0000000000000010
[ 36.091393] RAX:
ffffffffffffffda RBX:
000000000000ae80 RCX:
00007efdfe6d1aff
[ 36.091393] RDX:
0000000000000000 RSI:
000000000000ae80 RDI:
000000000000000c
[ 36.091394] RBP:
0000558f1609e220 R08:
0000558f13fb8190 R09:
00000000ffffffff
[ 36.091394] R10:
0000558f16b5e950 R11:
0000000000000246 R12:
0000000000000000
[ 36.091394] R13:
0000000000000001 R14:
0000000000000000 R15:
0000000000000000
[ 36.091396] </TASK>
[ 36.091397] Modules linked in: isofs nls_iso8859_1 kvm_intel joydev kvm input_leds serio_raw sch_fq_codel dm_multipath scsi_dh_rdac scsi_dh_emc scsi_dh_alua ipmi_devintf ipmi_msghandler drm msr ip_tables x_tables autofs4 btrfs blake2b_generic zstd_compress raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel virtio_net net_failover crypto_simd ahci xhci_pci cryptd psmouse virtio_blk libahci xhci_pci_renesas failover
[ 36.123271] ---[ end trace
db3c0ab5a48fabcc ]---
[ 36.123272] RIP: 0010:xaddw_ax_dx+0x9/0x10 [kvm]
[ 36.123319] Code: 00 0f bb d0 c3 cc cc cc cc 48 0f bb d0 c3 cc cc cc cc 0f 1f 80 00 00 00 00 0f c0 d0 c3 cc cc cc cc 66 0f c1 d0 c3 cc cc cc cc <0f> 1f 80 00 00 00 00 0f c1 d0 c3 cc cc cc cc 48 0f c1 d0 c3 cc cc
[ 36.123320] RSP: 0018:
ffffb1f541143c98 EFLAGS:
00000202
[ 36.123321] RAX:
0000000089abcdef RBX:
0000000000000001 RCX:
0000000000000000
[ 36.123321] RDX:
0000000076543210 RSI:
ffffffffc073c6d0 RDI:
0000000000000200
[ 36.123322] RBP:
ffffb1f541143ca0 R08:
ffff9f1803350a70 R09:
0000000000000002
[ 36.123322] R10:
ffff9f1803350a70 R11:
0000000000000000 R12:
ffff9f1803350a70
[ 36.123323] R13:
ffffffffc077fee0 R14:
0000000000000000 R15:
0000000000000000
[ 36.123323] FS:
00007efdfce8d640(0000) GS:
ffff9f187dd80000(0000) knlGS:
0000000000000000
[ 36.123324] CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
[ 36.123325] CR2:
0000000000000000 CR3:
0000000009b62002 CR4:
0000000000772ee0
[ 36.123327] PKRU:
55555554
[ 36.123328] Kernel panic - not syncing: Fatal exception in interrupt
[ 36.123410] Kernel Offset: 0x1400000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
[ 36.135305] ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
Fixes: 2c70af946767 ("x86: Use return-thunk in asm code")
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Co-developed-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Message-Id: <
20220713171241.184026-1-cascardo@canonical.com>
Tested-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
#define X8(x...) X4(x), X4(x)
#define X16(x...) X8(x), X8(x)
-#define NR_FASTOP (ilog2(sizeof(ulong)) + 1)
-#define FASTOP_SIZE (8 * (1 + HAS_KERNEL_IBT))
+#define NR_FASTOP (ilog2(sizeof(ulong)) + 1)
+#define RET_LENGTH (1 + (4 * IS_ENABLED(CONFIG_RETHUNK)) + \
+ IS_ENABLED(CONFIG_SLS))
+#define FASTOP_LENGTH (ENDBR_INSN_SIZE + 7 + RET_LENGTH)
+#define FASTOP_SIZE (8 << ((FASTOP_LENGTH > 8) & 1) << ((FASTOP_LENGTH > 16) & 1))
+static_assert(FASTOP_LENGTH <= FASTOP_SIZE);
struct opcode {
u64 flags;
* RET | JMP __x86_return_thunk [1,5 bytes; CONFIG_RETHUNK]
* INT3 [1 byte; CONFIG_SLS]
*/
-#define RET_LENGTH (1 + (4 * IS_ENABLED(CONFIG_RETHUNK)) + \
- IS_ENABLED(CONFIG_SLS))
#define SETCC_LENGTH (ENDBR_INSN_SIZE + 3 + RET_LENGTH)
#define SETCC_ALIGN (4 << ((SETCC_LENGTH > 4) & 1) << ((SETCC_LENGTH > 8) & 1))
static_assert(SETCC_LENGTH <= SETCC_ALIGN);
projects / kernel.git / commitdiff