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373b9338c9
Uprobe needs to fetch args into a percpu buffer, and then copy to ring
buffer to avoid non-atomic context problem.
Sometimes user-space strings, arrays can be very large, but the size of
percpu buffer is only page size. And store_trace_args() won't check
whether these data exceeds a single page or not, caused out-of-bounds
memory access.
It could be reproduced by following steps:
1. build kernel with CONFIG_KASAN enabled
2. save follow program as test.c
```
\#include <stdio.h>
\#include <stdlib.h>
\#include <string.h>
// If string length large than MAX_STRING_SIZE, the fetch_store_strlen()
// will return 0, cause __get_data_size() return shorter size, and
// store_trace_args() will not trigger out-of-bounds access.
// So make string length less than 4096.
\#define STRLEN 4093
void generate_string(char *str, int n)
{
int i;
for (i = 0; i < n; ++i)
{
char c = i % 26 + 'a';
str[i] = c;
}
str[n-1] = '\0';
}
void print_string(char *str)
{
printf("%s\n", str);
}
int main()
{
char tmp[STRLEN];
generate_string(tmp, STRLEN);
print_string(tmp);
return 0;
}
```
3. compile program
`gcc -o test test.c`
4. get the offset of `print_string()`
```
objdump -t test | grep -w print_string
0000000000401199 g F .text 000000000000001b print_string
```
5. configure uprobe with offset 0x1199
```
off=0x1199
cd /sys/kernel/debug/tracing/
echo "p /root/test:${off} arg1=+0(%di):ustring arg2=\$comm arg3=+0(%di):ustring"
> uprobe_events
echo 1 > events/uprobes/enable
echo 1 > tracing_on
```
6. run `test`, and kasan will report error.
==================================================================
BUG: KASAN: use-after-free in strncpy_from_user+0x1d6/0x1f0
Write of size 8 at addr ffff88812311c004 by task test/499CPU: 0 UID: 0 PID: 499 Comm: test Not tainted 6.12.0-rc3+ #18
Hardware name: Red Hat KVM, BIOS 1.16.0-4.al8 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x55/0x70
print_address_description.constprop.0+0x27/0x310
kasan_report+0x10f/0x120
? strncpy_from_user+0x1d6/0x1f0
strncpy_from_user+0x1d6/0x1f0
? rmqueue.constprop.0+0x70d/0x2ad0
process_fetch_insn+0xb26/0x1470
? __pfx_process_fetch_insn+0x10/0x10
? _raw_spin_lock+0x85/0xe0
? __pfx__raw_spin_lock+0x10/0x10
? __pte_offset_map+0x1f/0x2d0
? unwind_next_frame+0xc5f/0x1f80
? arch_stack_walk+0x68/0xf0
? is_bpf_text_address+0x23/0x30
? kernel_text_address.part.0+0xbb/0xd0
? __kernel_text_address+0x66/0xb0
? unwind_get_return_address+0x5e/0xa0
? __pfx_stack_trace_consume_entry+0x10/0x10
? arch_stack_walk+0xa2/0xf0
? _raw_spin_lock_irqsave+0x8b/0xf0
? __pfx__raw_spin_lock_irqsave+0x10/0x10
? depot_alloc_stack+0x4c/0x1f0
? _raw_spin_unlock_irqrestore+0xe/0x30
? stack_depot_save_flags+0x35d/0x4f0
? kasan_save_stack+0x34/0x50
? kasan_save_stack+0x24/0x50
? mutex_lock+0x91/0xe0
? __pfx_mutex_lock+0x10/0x10
prepare_uprobe_buffer.part.0+0x2cd/0x500
uprobe_dispatcher+0x2c3/0x6a0
? __pfx_uprobe_dispatcher+0x10/0x10
? __kasan_slab_alloc+0x4d/0x90
handler_chain+0xdd/0x3e0
handle_swbp+0x26e/0x3d0
? __pfx_handle_swbp+0x10/0x10
? uprobe_pre_sstep_notifier+0x151/0x1b0
irqentry_exit_to_user_mode+0xe2/0x1b0
asm_exc_int3+0x39/0x40
RIP: 0033:0x401199
Code: 01 c2 0f b6 45 fb 88 02 83 45 fc 01 8b 45 fc 3b 45 e4 7c b7 8b 45 e4 48 98 48 8d 50 ff 48 8b 45 e8 48 01 d0 ce
RSP: 002b:00007ffdf00576a8 EFLAGS: 00000206
RAX: 00007ffdf00576b0 RBX: 0000000000000000 RCX: 0000000000000ff2
RDX: 0000000000000ffc RSI: 0000000000000ffd RDI: 00007ffdf00576b0
RBP: 00007ffdf00586b0 R08: 00007feb2f9c0d20 R09: 00007feb2f9c0d20
R10: 0000000000000001 R11: 0000000000000202 R12: 0000000000401040
R13: 00007ffdf0058780 R14: 0000000000000000 R15: 0000000000000000
</TASK>
This commit enforces the buffer's maxlen less than a page-size to avoid
store_trace_args() out-of-memory access.
Link: https://lore.kernel.org/all/20241015060148.1108331-1-mqaio@linux.alibaba.com/
Fixes:
|
||
|---|---|---|
| .. | ||
| bpf | ||
| cgroup | ||
| configs | ||
| debug | ||
| dma | ||
| entry | ||
| events | ||
| futex | ||
| gcov | ||
| irq | ||
| kcsan | ||
| livepatch | ||
| locking | ||
| module | ||
| power | ||
| printk | ||
| rcu | ||
| sched | ||
| time | ||
| trace | ||
| .gitignore | ||
| acct.c | ||
| async.c | ||
| audit_fsnotify.c | ||
| audit_tree.c | ||
| audit_watch.c | ||
| audit.c | ||
| audit.h | ||
| auditfilter.c | ||
| auditsc.c | ||
| backtracetest.c | ||
| bounds.c | ||
| capability.c | ||
| cfi.c | ||
| compat.c | ||
| configs.c | ||
| context_tracking.c | ||
| cpu_pm.c | ||
| cpu.c | ||
| crash_core.c | ||
| crash_reserve.c | ||
| cred.c | ||
| delayacct.c | ||
| dma.c | ||
| elfcorehdr.c | ||
| exec_domain.c | ||
| exit.c | ||
| exit.h | ||
| extable.c | ||
| fail_function.c | ||
| fork.c | ||
| freezer.c | ||
| gen_kheaders.sh | ||
| groups.c | ||
| hung_task.c | ||
| iomem.c | ||
| irq_work.c | ||
| jump_label.c | ||
| kallsyms_internal.h | ||
| kallsyms_selftest.c | ||
| kallsyms_selftest.h | ||
| kallsyms.c | ||
| kcmp.c | ||
| Kconfig.freezer | ||
| Kconfig.hz | ||
| Kconfig.kexec | ||
| Kconfig.locks | ||
| Kconfig.preempt | ||
| kcov.c | ||
| kexec_core.c | ||
| kexec_elf.c | ||
| kexec_file.c | ||
| kexec_internal.h | ||
| kexec.c | ||
| kheaders.c | ||
| kprobes.c | ||
| ksyms_common.c | ||
| ksysfs.c | ||
| kthread.c | ||
| latencytop.c | ||
| Makefile | ||
| module_signature.c | ||
| notifier.c | ||
| nsproxy.c | ||
| padata.c | ||
| panic.c | ||
| params.c | ||
| pid_namespace.c | ||
| pid_sysctl.h | ||
| pid.c | ||
| profile.c | ||
| ptrace.c | ||
| range.c | ||
| reboot.c | ||
| regset.c | ||
| relay.c | ||
| resource_kunit.c | ||
| resource.c | ||
| rseq.c | ||
| scftorture.c | ||
| scs.c | ||
| seccomp.c | ||
| signal.c | ||
| smp.c | ||
| smpboot.c | ||
| smpboot.h | ||
| softirq.c | ||
| stackleak.c | ||
| stacktrace.c | ||
| static_call_inline.c | ||
| static_call.c | ||
| stop_machine.c | ||
| sys_ni.c | ||
| sys.c | ||
| sysctl-test.c | ||
| sysctl.c | ||
| task_work.c | ||
| taskstats.c | ||
| torture.c | ||
| tracepoint.c | ||
| tsacct.c | ||
| ucount.c | ||
| uid16.c | ||
| uid16.h | ||
| umh.c | ||
| up.c | ||
| user_namespace.c | ||
| user-return-notifier.c | ||
| user.c | ||
| usermode_driver.c | ||
| utsname_sysctl.c | ||
| utsname.c | ||
| vhost_task.c | ||
| vmcore_info.c | ||
| watch_queue.c | ||
| watchdog_buddy.c | ||
| watchdog_perf.c | ||
| watchdog.c | ||
| workqueue_internal.h | ||
| workqueue.c | ||