From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C66A130F7EA for ; Fri, 6 Mar 2026 07:24:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772781850; cv=none; b=GN4jrt479NblScb0+2Lpa5uznFpOSWy3bthrbkp1wT4z7jtE+cCYKCOEsee7rs4dssYmY6n8IShmR3qteLl6/qQHE2GGdkfbO1Rfk27M2zSKUzSlb9swn2qMy6HWxmaN4Q/bBsNQG9DT0jqhHPvFPCja7Zz5FKVhirQDoD2ZJCU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772781850; c=relaxed/simple; bh=wEIWJ2kTRcYulJ0H84vdMW1ci+rHr2L7Oquff4r6WNc=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=AWZxxcoPtqD6kyz10YZ8SoCQwu+8mr9vyQVBXMxakhCUktdr3SO9x5mVdLTa52vHPQQMlC0sCK+Sl2q8zd8oaYHQpOFYt0tfsA0rlRhrhJ/4p4v5HdVHvMI7HXKJ2VxWvdslQTp838kq+xOPcQpyEcCJeL64zHiWdR8n2LrU2J8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--kuniyu.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=R33urU+u; arc=none smtp.client-ip=209.85.214.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--kuniyu.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="R33urU+u" Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-2ae502a1dd9so67000425ad.3 for ; Thu, 05 Mar 2026 23:24:08 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1772781848; x=1773386648; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=VbhahzfFKovRH8YTa5ugBlDrP7nAiSq8irUd/ygeRHU=; b=R33urU+u9ZqduxqvxiXd2lUpagTig1W2567lM9ZgsquIsbVJ0JeEzLeKKIV9F1JM8d wHozP7yuo8WgshRECwuoSWgPr+zuTeHC5nX2GG1DfuH1SeVJQpjVEwzFycptHXHXYPiU RxeuG5AMg/cbSOQvHDs5AAhsW7G7/U87Uu/D4yhF0JaZyFATGeqtkt0f1U+tKMs2Mroh od5TxUy67siqf2Fp8Wn7AvqPXISegVgw1INMC7XdWEkBVCqfXBpT1TMbtNHbjrykXmO2 54zujlIyB2PgRUQo7gDMQmRxAOcqPEEY+WrQY65j/cmdqM5iY/0D3h54eAvsDS6UPAGE 1CIw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1772781848; x=1773386648; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=VbhahzfFKovRH8YTa5ugBlDrP7nAiSq8irUd/ygeRHU=; b=VzM+o5+iqcrJ34LRQDmcnnRqWsZ7zC6vdP3JO9jy3KhF2NTod3vCtC66yFimuzlSb5 oiKnyUh52g/QYEW+HzQAe5rdWPSDNGqqEju5kGabLHfebkPMP/Bw/WwUZwABkkpmZBrb 2hDOgdRZdvFb2/5D5JCklfix+aZmKE/M7cbwe5YXHhmIvTLQCWNSkTgymzKAGm7Dboa3 Y39YZqeTtQS/4dikkMWdbd3dkJc7UP/UJLZtop9Gb+6ZLqVWc7gHX+ScJc06gaCxIhKW FiAjg8+nMb+MVF8o3c22rqpbfgYnKoAv+Q3ixv+wEt14j0Os7HDmIEYGPsb6d6MgRJAX QXUA== X-Forwarded-Encrypted: i=1; AJvYcCXgSPZpIToSK1Ye0UlWdM3vOyBUvJZDf3lOAsyQDLojqtrDvG2TRcyRVsWN+4GEn5jsqzCnSt9jYCX/RtDSig==@vger.kernel.org X-Gm-Message-State: AOJu0YzT4RV8u85mvNTpUDnTTv34BkeBcAIHFbSmlfa8FgkE7HPA2F+E Ti7KD6bkQrka3do3mwXBI8cO6JECVU8c1AUMx949GiiwNS4lRaa+G3RFg/aQ1F02iXY5zA4OhKB aj/FJow== X-Received: from plq11.prod.google.com ([2002:a17:903:2f8b:b0:2ae:5e9d:8d47]) (user=kuniyu job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:d54f:b0:2ad:dd69:76a2 with SMTP id d9443c01a7336-2ae824dd0bcmr14991645ad.31.1772781847901; Thu, 05 Mar 2026 23:24:07 -0800 (PST) Date: Fri, 6 Mar 2026 07:24:02 +0000 Precedence: bulk X-Mailing-List: linux-wireless@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.53.0.473.g4a7958ca14-goog Message-ID: <20260306072405.3649474-1-kuniyu@google.com> Subject: [PATCH v2] wifi: mac80211: Fix static_branch_dec() underflow for aql_disable. From: Kuniyuki Iwashima To: Johannes Berg Cc: Lorenzo Bianconi , Kuniyuki Iwashima , Kuniyuki Iwashima , linux-wireless@vger.kernel.org, syzbot+feb9ce36a95341bb47a4@syzkaller.appspotmail.com Content-Type: text/plain; charset="UTF-8" syzbot reported static_branch_dec() underflow in aql_enable_write(). [0] The problem is that aql_enable_write() does not serialise concurrent write()s to the debugfs. aql_enable_write() checks static_key_false(&aql_disable.key) and later calls static_branch_inc() or static_branch_dec(), but the state may change between the two calls. aql_disable does not need to track inc/dec. Let's use static_branch_enable() and static_branch_disable(). [0]: val == 0 WARNING: kernel/jump_label.c:311 at __static_key_slow_dec_cpuslocked.part.0+0x107/0x120 kernel/jump_label.c:311, CPU#0: syz.1.3155/20288 Modules linked in: CPU: 0 UID: 0 PID: 20288 Comm: syz.1.3155 Tainted: G U L syzkaller #0 PREEMPT(full) Tainted: [U]=USER, [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026 RIP: 0010:__static_key_slow_dec_cpuslocked.part.0+0x107/0x120 kernel/jump_label.c:311 Code: f2 c9 ff 5b 5d c3 cc cc cc cc e8 54 f2 c9 ff 48 89 df e8 ac f9 ff ff eb ad e8 45 f2 c9 ff 90 0f 0b 90 eb a2 e8 3a f2 c9 ff 90 <0f> 0b 90 eb 97 48 89 df e8 5c 4b 33 00 e9 36 ff ff ff 0f 1f 80 00 RSP: 0018:ffffc9000b9f7c10 EFLAGS: 00010293 RAX: 0000000000000000 RBX: ffffffff9b3e5d40 RCX: ffffffff823c57b4 RDX: ffff8880285a0000 RSI: ffffffff823c5846 RDI: ffff8880285a0000 RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 000000000000000a R13: 1ffff9200173ef88 R14: 0000000000000001 R15: ffffc9000b9f7e98 FS: 00007f530dd726c0(0000) GS:ffff8881245e3000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000200000001140 CR3: 000000007cc4a000 CR4: 00000000003526f0 Call Trace: __static_key_slow_dec_cpuslocked kernel/jump_label.c:297 [inline] __static_key_slow_dec kernel/jump_label.c:321 [inline] static_key_slow_dec+0x7c/0xc0 kernel/jump_label.c:336 aql_enable_write+0x2b2/0x310 net/mac80211/debugfs.c:343 short_proxy_write+0x133/0x1a0 fs/debugfs/file.c:383 vfs_write+0x2aa/0x1070 fs/read_write.c:684 ksys_pwrite64 fs/read_write.c:793 [inline] __do_sys_pwrite64 fs/read_write.c:801 [inline] __se_sys_pwrite64 fs/read_write.c:798 [inline] __x64_sys_pwrite64+0x1eb/0x250 fs/read_write.c:798 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xc9/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f530cf9aeb9 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f530dd72028 EFLAGS: 00000246 ORIG_RAX: 0000000000000012 RAX: ffffffffffffffda RBX: 00007f530d215fa0 RCX: 00007f530cf9aeb9 RDX: 0000000000000003 RSI: 0000000000000000 RDI: 0000000000000010 RBP: 00007f530d008c1f R08: 0000000000000000 R09: 0000000000000000 R10: 4200000000000005 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f530d216038 R14: 00007f530d215fa0 R15: 00007ffde89fb978 Fixes: e908435e402a ("mac80211: introduce aql_enable node in debugfs") Reported-by: syzbot+feb9ce36a95341bb47a4@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/69a8979e.a70a0220.b118c.0025.GAE@google.com/ Signed-off-by: Kuniyuki Iwashima --- v2: Use static_key_enable/disable() v1: https://lore.kernel.org/linux-wireless/20260304204317.1921550-1-kuniyu@google.com/ --- net/mac80211/debugfs.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/net/mac80211/debugfs.c b/net/mac80211/debugfs.c index d02f07368c51..687a66cd4943 100644 --- a/net/mac80211/debugfs.c +++ b/net/mac80211/debugfs.c @@ -320,7 +320,6 @@ static ssize_t aql_enable_read(struct file *file, char __user *user_buf, static ssize_t aql_enable_write(struct file *file, const char __user *user_buf, size_t count, loff_t *ppos) { - bool aql_disabled = static_key_false(&aql_disable.key); char buf[3]; size_t len; @@ -335,15 +334,12 @@ static ssize_t aql_enable_write(struct file *file, const char __user *user_buf, if (len > 0 && buf[len - 1] == '\n') buf[len - 1] = 0; - if (buf[0] == '0' && buf[1] == '\0') { - if (!aql_disabled) - static_branch_inc(&aql_disable); - } else if (buf[0] == '1' && buf[1] == '\0') { - if (aql_disabled) - static_branch_dec(&aql_disable); - } else { + if (buf[0] == '0' && buf[1] == '\0') + static_branch_enable(&aql_disable); + else if (buf[0] == '1' && buf[1] == '\0') + static_branch_disable(&aql_disable); + else return -EINVAL; - } return count; } -- 2.53.0.473.g4a7958ca14-goog