6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiri Olsa [ Upstream commit 014fbe5902dccdaef69114abdcdb15e3dbe55e34 ] The new callchain_finalize function calls the build-id retrieval (if needed) and zeroes the buffer. This makes things easier for preemption fix in following change. Signed-off-by: Jiri Olsa Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20260803210149.296496-8-jolsa@kernel.org Stable-dep-of: f5d242825ca4 ("bpf: Clear buf on error in __bpf_get_task_stack") Signed-off-by: Sasha Levin --- kernel/bpf/stackmap.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 933edcbb92f56..8e4a716410494 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -644,16 +644,31 @@ static u32 callchain_store(struct perf_callchain_entry *trace, void *buf, return trace_nr; } +static long callchain_finalize(void *buf, u32 size, u32 trace_nr, u32 elem_size, + u64 flags, bool may_fault) +{ + bool user_build_id = flags & BPF_F_USER_BUILD_ID; + bool user = flags & BPF_F_USER_STACK; + u32 copy_len = trace_nr * elem_size; + + if (user_build_id) + stack_map_get_build_id_offset(buf, trace_nr, user, may_fault); + + if (size > copy_len) + memset(buf + copy_len, 0, size - copy_len); + return copy_len; +} + static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, struct perf_callchain_entry *trace_in, void *buf, u32 size, u64 flags, bool may_fault) { - u32 trace_nr, copy_len, elem_size, max_depth; bool user_build_id = flags & BPF_F_USER_BUILD_ID; bool crosstask = task && task != current; u32 skip = flags & BPF_F_SKIP_FIELD_MASK; bool user = flags & BPF_F_USER_STACK; struct perf_callchain_entry *trace; + u32 trace_nr, elem_size, max_depth; bool kernel = !user; int err = -EINVAL; @@ -703,19 +718,13 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, } trace_nr = callchain_store(trace, buf, elem_size, flags); - copy_len = trace_nr * elem_size; /* trace should not be dereferenced after this point */ if (may_fault) rcu_read_unlock(); preempt_enable(); - if (user_build_id) - stack_map_get_build_id_offset(buf, trace_nr, user, may_fault); - - if (size > copy_len) - memset(buf + copy_len, 0, size - copy_len); - return copy_len; + return callchain_finalize(buf, size, trace_nr, elem_size, flags, may_fault); err_fault: err = -EFAULT; -- 2.53.0