6.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Kumar Kartikeya Dwivedi memxor@gmail.com
[ Upstream commit d090326860096df9dac6f27cff76d3f8df44d4f1 ]
Add a warning to ensure RCU lock is held around tree lookup, and then fix one of the invocations in bpf_stack_walker. The program has an active stack frame and won't disappear. Use the opportunity to remove unneeded invocation of is_bpf_text_address.
Fixes: f18b03fabaa9 ("bpf: Implement BPF exceptions") Reviewed-by: Emil Tsalapatis emil@etsalapatis.com Signed-off-by: Kumar Kartikeya Dwivedi memxor@gmail.com Link: https://lore.kernel.org/r/20250703204818.925464-5-memxor@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/core.c | 5 ++++- kernel/bpf/helpers.c | 11 +++++++++-- 2 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index c20babbf998f..93e49b0c218b 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -778,7 +778,10 @@ bool is_bpf_text_address(unsigned long addr)
struct bpf_prog *bpf_prog_ksym_find(unsigned long addr) { - struct bpf_ksym *ksym = bpf_ksym_find(addr); + struct bpf_ksym *ksym; + + WARN_ON_ONCE(!rcu_read_lock_held()); + ksym = bpf_ksym_find(addr);
return ksym && ksym->prog ? container_of(ksym, struct bpf_prog_aux, ksym)->prog : diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 52d02bc0abb2..3312442bc389 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2864,9 +2864,16 @@ static bool bpf_stack_walker(void *cookie, u64 ip, u64 sp, u64 bp) struct bpf_throw_ctx *ctx = cookie; struct bpf_prog *prog;
- if (!is_bpf_text_address(ip)) - return !ctx->cnt; + /* + * The RCU read lock is held to safely traverse the latch tree, but we + * don't need its protection when accessing the prog, since it has an + * active stack frame on the current stack trace, and won't disappear. + */ + rcu_read_lock(); prog = bpf_prog_ksym_find(ip); + rcu_read_unlock(); + if (!prog) + return !ctx->cnt; ctx->cnt++; if (bpf_is_subprog(prog)) return true;