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[173.180.147.14]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-31e662f4953sm637253a91.34.2025.07.24.00.16.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Jul 2025 00:16:22 -0700 (PDT) From: Moon Hee Lee To: johannes@sipsolutions.net Cc: linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org, linux-kernel-mentees@lists.linux.dev, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com, syzbot+d6ccd49ae046542a0641@syzkaller.appspotmail.com, skhan@linuxfoundation.org, david.hunter.linux@gmail.com, Moon Hee Lee Subject: [PATCH wireless-next] wifi: mac80211: fix use-after-free risk in sta debugfs removal Date: Thu, 24 Jul 2025 00:15:56 -0700 Message-ID: <20250724071555.442634-2-moonhee.lee.ca@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel-mentees@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit A NULL pointer dereference may occur in ieee80211_sta_debugfs_remove() when debugfs_remove_recursive() is called on a dentry whose inode has already been freed. This can happen due to a race between STA teardown and debugfs cleanup. Fix this by checking that both sta->debugfs_dir and its d_inode are valid before invoking debugfs_remove_recursive(). This avoids the crash reported in syzbot bug: wlan1: send auth to aa:09:b7:99:c0:d7 (try 2/3) wlan1: send auth to aa:09:b7:99:c0:d7 (try 3/3) wlan1: authentication with aa:09:b7:99:c0:d7 timed out Oops: general protection fault, probably for non-canonical address 0xdffffc0000000029: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000148-0x000000000000014f] CPU: 0 UID: 0 PID: 171 Comm: kworker/u4:4 Not tainted 6.16.0-rc7-syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Workqueue: events_unbound cfg80211_wiphy_work RIP: 0010:kasan_byte_accessible+0x12/0x30 mm/kasan/generic.c:199 Code: 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 0f 1f 00 48 c1 ef 03 48 b8 00 00 00 00 00 fc ff df <0f> b6 04 07 3c 08 0f 92 c0 c3 cc cc cc cc cc 66 66 66 66 66 66 2e RSP: 0018:ffffc90001977400 EFLAGS: 00010202 RAX: dffffc0000000000 RBX: ffffffff8b713286 RCX: ca5c1933e35f3700 RDX: 0000000000000000 RSI: ffffffff8b713286 RDI: 0000000000000029 RBP: ffffffff824067f0 R08: 0000000000000001 R09: 0000000000000000 R10: dffffc0000000000 R11: ffffed10085cf24c R12: 0000000000000000 R13: 0000000000000148 R14: 0000000000000148 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff88808d218000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b2f55ffff CR3: 000000005030a000 CR4: 0000000000352ef0 Call Trace: __kasan_check_byte+0x12/0x40 mm/kasan/common.c:556 kasan_check_byte include/linux/kasan.h:399 [inline] lock_acquire+0x8d/0x360 kernel/locking/lockdep.c:5845 down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577 inode_lock include/linux/fs.h:869 [inline] simple_recursive_removal+0x90/0x690 fs/libfs.c:616 debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:805 ieee80211_sta_debugfs_remove+0x40/0x70 net/mac80211/debugfs_sta.c:1279 __sta_info_destroy_part2+0x352/0x450 net/mac80211/sta_info.c:1501 __sta_info_destroy net/mac80211/sta_info.c:1517 [inline] sta_info_destroy_addr+0xf5/0x140 net/mac80211/sta_info.c:1529 ieee80211_destroy_auth_data+0x12d/0x260 net/mac80211/mlme.c:4597 ieee80211_sta_work+0x11cf/0x3600 net/mac80211/mlme.c:8310 cfg80211_wiphy_work+0x2df/0x460 net/wireless/core.c:435 process_one_work kernel/workqueue.c:3238 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402 kthread+0x70e/0x8a0 kernel/kthread.c:464 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 Reported-by: syzbot+d6ccd49ae046542a0641@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=d6ccd49ae046542a0641 Fixes: fc4a25c5b741 ("mac80211: remove sta_info debugfs sub-struct") Tested-by: syzbot+d6ccd49ae046542a0641@syzkaller.appspotmail.com Signed-off-by: Moon Hee Lee --- net/mac80211/debugfs_sta.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/mac80211/debugfs_sta.c b/net/mac80211/debugfs_sta.c index 49061bd4151b..912b69abab52 100644 --- a/net/mac80211/debugfs_sta.c +++ b/net/mac80211/debugfs_sta.c @@ -1276,7 +1276,8 @@ void ieee80211_sta_debugfs_add(struct sta_info *sta) void ieee80211_sta_debugfs_remove(struct sta_info *sta) { - debugfs_remove_recursive(sta->debugfs_dir); + if (sta->debugfs_dir && sta->debugfs_dir->d_inode) + debugfs_remove_recursive(sta->debugfs_dir); sta->debugfs_dir = NULL; } -- 2.43.0