From db807e5ef8eea6948bb4993466623046f52d3056 Mon Sep 17 00:00:00 2001 From: Taehee Yoo Date: Tue, 20 May 2025 07:11:55 +0000 Subject: [PATCH] eth: bnxt: fix deadlock when xdp is attached or detached When xdp is attached or detached, dev->ndo_bpf() is called by do_setlink(), and it acquires netdev_lock() if needed. Unlike other drivers, the bnxt driver is protected by netdev_lock while xdp is attached/detached because it sets dev->request_ops_lock to true. So, the bnxt_xdp(), that is callback of ->ndo_bpf should not acquire netdev_lock(). But the xdp_features_{set | clear}_redirect_target() was changed to acquire netdev_lock() internally. It causes a deadlock. To fix this problem, bnxt driver should use xdp_features_{set | clear}_redirect_target_locked() instead. Splat looks like: ============================================ WARNING: possible recursive locking detected 6.15.0-rc6+ #1 Not tainted -------------------------------------------- bpftool/1745 is trying to acquire lock: ffff888131b85038 (&dev->lock){+.+.}-{4:4}, at: xdp_features_set_redirect_target+0x1f/0x80 but task is already holding lock: ffff888131b85038 (&dev->lock){+.+.}-{4:4}, at: do_setlink.constprop.0+0x24e/0x35d0 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&dev->lock); lock(&dev->lock); *** DEADLOCK *** May be due to missing lock nesting notation 3 locks held by bpftool/1745: #0: ffffffffa56131c8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_setlink+0x1fe/0x570 #1: ffffffffaafa75a0 (&net->rtnl_mutex){+.+.}-{4:4}, at: rtnl_setlink+0x236/0x570 #2: ffff888131b85038 (&dev->lock){+.+.}-{4:4}, at: do_setlink.constprop.0+0x24e/0x35d0 stack backtrace: CPU: 1 UID: 0 PID: 1745 Comm: bpftool Not tainted 6.15.0-rc6+ #1 PREEMPT(undef) Hardware name: ASUS System Product Name/PRIME Z690-P D4, BIOS 0603 11/01/2021 Call Trace: dump_stack_lvl+0x7a/0xd0 print_deadlock_bug+0x294/0x3d0 __lock_acquire+0x153b/0x28f0 lock_acquire+0x184/0x340 ? xdp_features_set_redirect_target+0x1f/0x80 __mutex_lock+0x1ac/0x18a0 ? xdp_features_set_redirect_target+0x1f/0x80 ? xdp_features_set_redirect_target+0x1f/0x80 ? __pfx_bnxt_rx_page_skb+0x10/0x10 [bnxt_en ? __pfx___mutex_lock+0x10/0x10 ? __pfx_netdev_update_features+0x10/0x10 ? bnxt_set_rx_skb_mode+0x284/0x540 [bnxt_en ? __pfx_bnxt_set_rx_skb_mode+0x10/0x10 [bnxt_en ? xdp_features_set_redirect_target+0x1f/0x80 xdp_features_set_redirect_target+0x1f/0x80 bnxt_xdp+0x34e/0x730 [bnxt_en 11cbcce8fa11cff1dddd7ef358d6219e4ca9add3] dev_xdp_install+0x3f4/0x830 ? __pfx_bnxt_xdp+0x10/0x10 [bnxt_en 11cbcce8fa11cff1dddd7ef358d6219e4ca9add3] ? __pfx_dev_xdp_install+0x10/0x10 dev_xdp_attach+0x560/0xf70 dev_change_xdp_fd+0x22d/0x280 do_setlink.constprop.0+0x2989/0x35d0 ? __pfx_do_setlink.constprop.0+0x10/0x10 ? lock_acquire+0x184/0x340 ? find_held_lock+0x32/0x90 ? rtnl_setlink+0x236/0x570 ? rcu_is_watching+0x11/0xb0 ? trace_contention_end+0xdc/0x120 ? __mutex_lock+0x946/0x18a0 ? __pfx___mutex_lock+0x10/0x10 ? __lock_acquire+0xa95/0x28f0 ? rcu_is_watching+0x11/0xb0 ? rcu_is_watching+0x11/0xb0 ? cap_capable+0x172/0x350 rtnl_setlink+0x2cd/0x570 Fixes: 03df156dd3a6 ("xdp: double protect netdev->xdp_flags with netdev->lock") Signed-off-by: Taehee Yoo Reviewed-by: Simon Horman Reviewed-by: Michael Chan Link: https://patch.msgid.link/20250520071155.2462843-1-ap420073@gmail.com Signed-off-by: Jakub Kicinski --- drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c index e675611777b5..4a6d8cb9f970 100644 --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c @@ -425,9 +425,9 @@ static int bnxt_xdp_set(struct bnxt *bp, struct bpf_prog *prog) if (prog) { bnxt_set_rx_skb_mode(bp, true); - xdp_features_set_redirect_target(dev, true); + xdp_features_set_redirect_target_locked(dev, true); } else { - xdp_features_clear_redirect_target(dev); + xdp_features_clear_redirect_target_locked(dev); bnxt_set_rx_skb_mode(bp, false); } bp->tx_nr_rings_xdp = tx_xdp; -- 2.50.1