diff options
Diffstat (limited to 'kernel/bpf/stackmap.c')
| -rw-r--r-- | kernel/bpf/stackmap.c | 33 |
1 files changed, 23 insertions, 10 deletions
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index f7e8d766d128..a19126f5db02 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -522,12 +522,14 @@ static int stackid_init(struct stackid *stackid, struct bpf_map *map, u32 skip = flags & BPF_F_SKIP_FIELD_MASK; u32 max_depth; + max_depth = stack_map_calculate_max_depth(map->value_size, stack_map_data_size(map), flags); + /* trace_nr can be above max_depth and max_depth below skip: clamp first */ + trace_nr = min_t(u32, trace_nr, max_depth); if (trace_nr <= skip) /* skipping more than usable stack trace */ return -EFAULT; - max_depth = stack_map_calculate_max_depth(map->value_size, stack_map_data_size(map), flags); - stackid->nr = min_t(u32, trace_nr - skip, max_depth - skip); + stackid->nr = trace_nr - skip; stackid->len = stackid->nr * sizeof(u64); stackid->ips = trace->ip + skip; stackid->hash = jhash2((const u32 *)stackid->ips, stackid->len / sizeof(u32), 0); @@ -642,7 +644,8 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, /* couldn't fetch the stack trace */ return -EFAULT; - err = stackid_fastpath(&stackid, map, trace, trace->nr, flags); + /* the entry is released already, an NMI can change trace->nr */ + err = stackid_fastpath(&stackid, map, trace, READ_ONCE(trace->nr), flags); if (err != -ENOENT) return err; @@ -822,14 +825,20 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, crosstask, false, 0); } - if (unlikely(!trace) || trace->nr < skip) { - if (may_fault) - rcu_read_unlock(); - preempt_enable(); - goto err_fault; - } + if (unlikely(!trace)) + goto err_unlock; - trace_nr = callchain_store(trace, trace->nr, buf, elem_size, flags); + /* + * trace->nr can be above max_depth. The per-CPU entry is released + * already: a tracing program or an NMI which takes a callchain in the + * same context before the copy below reuses it. And the unwinders of + * PowerPC store context markers on top of max_depth. + */ + trace_nr = min_t(u32, READ_ONCE(trace->nr), max_depth); + if (trace_nr < skip) + goto err_unlock; + + trace_nr = callchain_store(trace, trace_nr, buf, elem_size, flags); /* trace should not be dereferenced after this point */ if (may_fault) @@ -838,6 +847,10 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, return callchain_finalize(buf, size, trace_nr, elem_size, flags, may_fault); +err_unlock: + if (may_fault) + rcu_read_unlock(); + preempt_enable(); err_fault: err = -EFAULT; clear: |