Hi,
We observed a crash "KFENCE: use-after-free in __skb_clone" during fuzzing.
It's a frequent occurrance in aarch64 and the codepath is always the
same,but cannot be reproduced in x86_64.
Detailed crash information is as follows:
-----------------------------------------
- Kernel commit:
89bf6e28373beef
- Crash report:
BUG: KFENCE: use-after-free read in __skb_clone+0x214/0x280
Use-after-free read at 0xffff00022250306f (in kfence-#250):
__skb_clone+0x214/0x280
skb_clone+0xb4/0x180
bpf_clone_redirect+0x60/0x190
bpf_prog_207b739f41707f89+0x88/0xb8
bpf_test_run+0x2dc/0x4fc
bpf_prog_test_run_skb+0x4ac/0x7d0
__sys_bpf+0x700/0x1020
__arm64_sys_bpf+0x4c/0x60
invoke_syscall+0x64/0x190
el0_svc_common.constprop.0+0x88/0x200
do_el0_svc+0x3c/0x50
el0_svc+0x68/0xd0
el0t_64_sync_handler+0xb4/0x130
el0t_64_sync+0x16c/0x170
kfence-#250: 0xffff000222503000-0xffff00022250318e, size=399,
cache=kmalloc-512
allocated by task 2970 on cpu 0 at 65.981345s:
bpf_test_init.isra.0+0x68/0x100
bpf_prog_test_run_skb+0x114/0x7d0
__sys_bpf+0x700/0x1020
__arm64_sys_bpf+0x4c/0x60
invoke_syscall+0x64/0x190
el0_svc_common.constprop.0+0x88/0x200
do_el0_svc+0x3c/0x50
el0_svc+0x68/0xd0
el0t_64_sync_handler+0xb4/0x130
el0t_64_sync+0x16c/0x170
CPU: 0 PID: 2970 Comm: syz Tainted: G B W
6.1.0-rc2-next-20221025 #140
Hardware name: linux,dummy-virt (DT)
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : __skb_clone+0x214/0x280
lr : __skb_clone+0x208/0x280
sp : ffff80000fc37630
x29: ffff80000fc37630 x28: ffff80000fc37bd0 x27: ffff80000fc37720
x26: ffff000222503000 x25: 000000000000028f x24: ffff0000d0898d5c
x23: ffff0000d08997c0 x22: ffff0000d089977e x21: ffff00022250304f
x20: ffff0000d0899700 x19: ffff0000d0898c80 x18: 0000000000000000
x17: ffff800008379bbc x16: ffff800008378ee0 x15: ffff800008379bbc
x14: ffff800008378ee0 x13: 0040004effff0008 x12: ffff6000444a060f
x11: 1fffe000444a060e x10: ffff6000444a060e x9 : dfff800000000000
x8 : ffff000222503072 x7 : 00009fffbbb5f9f3 x6 : 0000000000000002
x5 : ffff00022250306f x4 : ffff6000444a060f x3 : ffff8000096fb2a8
x2 : 0000000000000001 x1 : ffff00022250306f x0 : 0000000000000001
Call trace:
__skb_clone+0x214/0x280
skb_clone+0xb4/0x180
bpf_clone_redirect+0x60/0x190
bpf_prog_207b739f41707f89+0x88/0xb8
bpf_test_run+0x2dc/0x4fc
bpf_prog_test_run_skb+0x4ac/0x7d0
__sys_bpf+0x700/0x1020
__arm64_sys_bpf+0x4c/0x60
invoke_syscall+0x64/0x190
el0_svc_common.constprop.0+0x88/0x200
do_el0_svc+0x3c/0x50
el0_svc+0x68/0xd0
el0t_64_sync_handler+0xb4/0x130
el0t_64_sync+0x16c/0x170
Do you have any suggestion for this issue?
Thank you.
Best Regards,
Baisong Zhong