s390/ftrace: fix ftrace_update_ftrace_func implementation
s390 enforces DYNAMIC_FTRACE if FUNCTION_TRACER is selected.
At the same time implementation of ftrace_caller is not compliant with
HAVE_DYNAMIC_FTRACE since it doesn't provide implementation of
ftrace_update_ftrace_func() and calls ftrace_trace_function() directly.
The subtle difference is that during ftrace code patching ftrace
replaces function tracer via ftrace_update_ftrace_func() and activates
it back afterwards. Unexpected direct calls to ftrace_trace_function()
during ftrace code patching leads to nullptr-dereferences when tracing
is activated for one of functions which are used during code patching.
Those function currently are:
copy_from_kernel_nofault()
copy_from_kernel_nofault_allowed()
preempt_count_sub() [with debug_defconfig]
preempt_count_add() [with debug_defconfig]
Corresponding KASAN report:
BUG: KASAN: nullptr-dereference in function_trace_call+0x316/0x3b0
Read of size 4 at addr 0000000000001e08 by task migration/0/15
CPU: 0 PID: 15 Comm: migration/0 Tainted: G B 5.13.0-41423-g08316af3644d
Hardware name: IBM 3906 M04 704 (LPAR)
Stopper: multi_cpu_stop+0x0/0x3e0 <- stop_machine_cpuslocked+0x1e4/0x218
Call Trace:
[<0000000001f77caa>] show_stack+0x16a/0x1d0
[<0000000001f8de42>] dump_stack+0x15a/0x1b0
[<0000000001f81d56>] print_address_description.constprop.0+0x66/0x2e0
[<000000000082b0ca>] kasan_report+0x152/0x1c0
[<00000000004cfd8e>] function_trace_call+0x316/0x3b0
[<0000000001fb7082>] ftrace_caller+0x7a/0x7e
[<00000000006bb3e6>] copy_from_kernel_nofault_allowed+0x6/0x10
[<00000000006bb42e>] copy_from_kernel_nofault+0x3e/0xd0
[<000000000014605c>] ftrace_make_call+0xb4/0x1f8
[<000000000047a1b4>] ftrace_replace_code+0x134/0x1d8
[<000000000047a6e0>] ftrace_modify_all_code+0x120/0x1d0
[<000000000047a7ec>] __ftrace_modify_code+0x5c/0x78
[<000000000042395c>] multi_cpu_stop+0x224/0x3e0
[<0000000000423212>] cpu_stopper_thread+0x33a/0x5a0
[<0000000000243ff2>] smpboot_thread_fn+0x302/0x708
[<00000000002329ea>] kthread+0x342/0x408
[<00000000001066b2>] __ret_from_fork+0x92/0xf0
[<0000000001fb57fa>] ret_from_fork+0xa/0x30
The buggy address belongs to the page:
page:(____ptrval____) refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1
flags: 0x1ffff00000001000(reserved|node=0|zone=0|lastcpupid=0x1ffff)
raw: 1ffff00000001000 0000040000000048 0000040000000048 0000000000000000
raw: 0000000000000000 0000000000000000 ffffffff00000001 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
0000000000001d00: f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7
0000000000001d80: f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7
>0000000000001e00: f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7
^
0000000000001e80: f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7
0000000000001f00: f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7 f7
==================================================================
To fix that introduce ftrace_func callback to be called from
ftrace_caller and update it in ftrace_update_ftrace_func().
Fixes: 4cc9bed034d1 ("[S390] cleanup ftrace backend functions")
Cc: stable@vger.kernel.org
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
3 files changed
