From 647e60f11d6a81574d5146837ed795627fa3c40f Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Sun, 26 May 2024 15:52:19 +0200 Subject: [PATCH] 4.19-stable patches added patches: nilfs2-fix-potential-hang-in-nilfs_detach_log_writer.patch nilfs2-fix-unexpected-freezing-of-nilfs_segctor_sync.patch --- ...tial-hang-in-nilfs_detach_log_writer.patch | 110 ++++++++++++++++++ ...ected-freezing-of-nilfs_segctor_sync.patch | 82 +++++++++++++ queue-4.19/series | 2 + 3 files changed, 194 insertions(+) create mode 100644 queue-4.19/nilfs2-fix-potential-hang-in-nilfs_detach_log_writer.patch create mode 100644 queue-4.19/nilfs2-fix-unexpected-freezing-of-nilfs_segctor_sync.patch diff --git a/queue-4.19/nilfs2-fix-potential-hang-in-nilfs_detach_log_writer.patch b/queue-4.19/nilfs2-fix-potential-hang-in-nilfs_detach_log_writer.patch new file mode 100644 index 00000000000..aa342ebc295 --- /dev/null +++ b/queue-4.19/nilfs2-fix-potential-hang-in-nilfs_detach_log_writer.patch @@ -0,0 +1,110 @@ +From eb85dace897c5986bc2f36b3c783c6abb8a4292e Mon Sep 17 00:00:00 2001 +From: Ryusuke Konishi +Date: Mon, 20 May 2024 22:26:21 +0900 +Subject: nilfs2: fix potential hang in nilfs_detach_log_writer() + +From: Ryusuke Konishi + +commit eb85dace897c5986bc2f36b3c783c6abb8a4292e upstream. + +Syzbot has reported a potential hang in nilfs_detach_log_writer() called +during nilfs2 unmount. + +Analysis revealed that this is because nilfs_segctor_sync(), which +synchronizes with the log writer thread, can be called after +nilfs_segctor_destroy() terminates that thread, as shown in the call trace +below: + +nilfs_detach_log_writer + nilfs_segctor_destroy + nilfs_segctor_kill_thread --> Shut down log writer thread + flush_work + nilfs_iput_work_func + nilfs_dispose_list + iput + nilfs_evict_inode + nilfs_transaction_commit + nilfs_construct_segment (if inode needs sync) + nilfs_segctor_sync --> Attempt to synchronize with + log writer thread + *** DEADLOCK *** + +Fix this issue by changing nilfs_segctor_sync() so that the log writer +thread returns normally without synchronizing after it terminates, and by +forcing tasks that are already waiting to complete once after the thread +terminates. + +The skipped inode metadata flushout will then be processed together in the +subsequent cleanup work in nilfs_segctor_destroy(). + +Link: https://lkml.kernel.org/r/20240520132621.4054-4-konishi.ryusuke@gmail.com +Signed-off-by: Ryusuke Konishi +Reported-by: syzbot+e3973c409251e136fdd0@syzkaller.appspotmail.com +Closes: https://syzkaller.appspot.com/bug?extid=e3973c409251e136fdd0 +Tested-by: Ryusuke Konishi +Cc: +Cc: "Bai, Shuangpeng" +Signed-off-by: Andrew Morton +Signed-off-by: Greg Kroah-Hartman +--- + fs/nilfs2/segment.c | 21 ++++++++++++++++++--- + 1 file changed, 18 insertions(+), 3 deletions(-) + +--- a/fs/nilfs2/segment.c ++++ b/fs/nilfs2/segment.c +@@ -2229,6 +2229,14 @@ static int nilfs_segctor_sync(struct nil + for (;;) { + set_current_state(TASK_INTERRUPTIBLE); + ++ /* ++ * Synchronize only while the log writer thread is alive. ++ * Leave flushing out after the log writer thread exits to ++ * the cleanup work in nilfs_segctor_destroy(). ++ */ ++ if (!sci->sc_task) ++ break; ++ + if (atomic_read(&wait_req.done)) { + err = wait_req.err; + break; +@@ -2244,7 +2252,7 @@ static int nilfs_segctor_sync(struct nil + return err; + } + +-static void nilfs_segctor_wakeup(struct nilfs_sc_info *sci, int err) ++static void nilfs_segctor_wakeup(struct nilfs_sc_info *sci, int err, bool force) + { + struct nilfs_segctor_wait_request *wrq, *n; + unsigned long flags; +@@ -2252,7 +2260,7 @@ static void nilfs_segctor_wakeup(struct + spin_lock_irqsave(&sci->sc_wait_request.lock, flags); + list_for_each_entry_safe(wrq, n, &sci->sc_wait_request.head, wq.entry) { + if (!atomic_read(&wrq->done) && +- nilfs_cnt32_ge(sci->sc_seq_done, wrq->seq)) { ++ (force || nilfs_cnt32_ge(sci->sc_seq_done, wrq->seq))) { + wrq->err = err; + atomic_set(&wrq->done, 1); + } +@@ -2392,7 +2400,7 @@ static void nilfs_segctor_notify(struct + if (mode == SC_LSEG_SR) { + sci->sc_state &= ~NILFS_SEGCTOR_COMMIT; + sci->sc_seq_done = sci->sc_seq_accepted; +- nilfs_segctor_wakeup(sci, err); ++ nilfs_segctor_wakeup(sci, err, false); + sci->sc_flush_request = 0; + } else { + if (mode == SC_FLUSH_FILE) +@@ -2774,6 +2782,13 @@ static void nilfs_segctor_destroy(struct + || sci->sc_seq_request != sci->sc_seq_done); + spin_unlock(&sci->sc_state_lock); + ++ /* ++ * Forcibly wake up tasks waiting in nilfs_segctor_sync(), which can ++ * be called from delayed iput() via nilfs_evict_inode() and can race ++ * with the above log writer thread termination. ++ */ ++ nilfs_segctor_wakeup(sci, 0, true); ++ + if (flush_work(&sci->sc_iput_work)) + flag = true; + diff --git a/queue-4.19/nilfs2-fix-unexpected-freezing-of-nilfs_segctor_sync.patch b/queue-4.19/nilfs2-fix-unexpected-freezing-of-nilfs_segctor_sync.patch new file mode 100644 index 00000000000..e261a6ead87 --- /dev/null +++ b/queue-4.19/nilfs2-fix-unexpected-freezing-of-nilfs_segctor_sync.patch @@ -0,0 +1,82 @@ +From 936184eadd82906992ff1f5ab3aada70cce44cee Mon Sep 17 00:00:00 2001 +From: Ryusuke Konishi +Date: Mon, 20 May 2024 22:26:20 +0900 +Subject: nilfs2: fix unexpected freezing of nilfs_segctor_sync() + +From: Ryusuke Konishi + +commit 936184eadd82906992ff1f5ab3aada70cce44cee upstream. + +A potential and reproducible race issue has been identified where +nilfs_segctor_sync() would block even after the log writer thread writes a +checkpoint, unless there is an interrupt or other trigger to resume log +writing. + +This turned out to be because, depending on the execution timing of the +log writer thread running in parallel, the log writer thread may skip +responding to nilfs_segctor_sync(), which causes a call to schedule() +waiting for completion within nilfs_segctor_sync() to lose the opportunity +to wake up. + +The reason why waking up the task waiting in nilfs_segctor_sync() may be +skipped is that updating the request generation issued using a shared +sequence counter and adding an wait queue entry to the request wait queue +to the log writer, are not done atomically. There is a possibility that +log writing and request completion notification by nilfs_segctor_wakeup() +may occur between the two operations, and in that case, the wait queue +entry is not yet visible to nilfs_segctor_wakeup() and the wake-up of +nilfs_segctor_sync() will be carried over until the next request occurs. + +Fix this issue by performing these two operations simultaneously within +the lock section of sc_state_lock. Also, following the memory barrier +guidelines for event waiting loops, move the call to set_current_state() +in the same location into the event waiting loop to ensure that a memory +barrier is inserted just before the event condition determination. + +Link: https://lkml.kernel.org/r/20240520132621.4054-3-konishi.ryusuke@gmail.com +Fixes: 9ff05123e3bf ("nilfs2: segment constructor") +Signed-off-by: Ryusuke Konishi +Tested-by: Ryusuke Konishi +Cc: +Cc: "Bai, Shuangpeng" +Signed-off-by: Andrew Morton +Signed-off-by: Greg Kroah-Hartman +--- + fs/nilfs2/segment.c | 17 +++++++++++++---- + 1 file changed, 13 insertions(+), 4 deletions(-) + +--- a/fs/nilfs2/segment.c ++++ b/fs/nilfs2/segment.c +@@ -2207,19 +2207,28 @@ static int nilfs_segctor_sync(struct nil + struct nilfs_segctor_wait_request wait_req; + int err = 0; + +- spin_lock(&sci->sc_state_lock); + init_wait(&wait_req.wq); + wait_req.err = 0; + atomic_set(&wait_req.done, 0); ++ init_waitqueue_entry(&wait_req.wq, current); ++ ++ /* ++ * To prevent a race issue where completion notifications from the ++ * log writer thread are missed, increment the request sequence count ++ * "sc_seq_request" and insert a wait queue entry using the current ++ * sequence number into the "sc_wait_request" queue at the same time ++ * within the lock section of "sc_state_lock". ++ */ ++ spin_lock(&sci->sc_state_lock); + wait_req.seq = ++sci->sc_seq_request; ++ add_wait_queue(&sci->sc_wait_request, &wait_req.wq); + spin_unlock(&sci->sc_state_lock); + +- init_waitqueue_entry(&wait_req.wq, current); +- add_wait_queue(&sci->sc_wait_request, &wait_req.wq); +- set_current_state(TASK_INTERRUPTIBLE); + wake_up(&sci->sc_wait_daemon); + + for (;;) { ++ set_current_state(TASK_INTERRUPTIBLE); ++ + if (atomic_read(&wait_req.done)) { + err = wait_req.err; + break; diff --git a/queue-4.19/series b/queue-4.19/series index 9f9b18cb08a..6bb32bcd7e3 100644 --- a/queue-4.19/series +++ b/queue-4.19/series @@ -1,4 +1,6 @@ speakup-fix-sizeof-vs-array_size-bug.patch ring-buffer-fix-a-race-between-readers-and-resize-checks.patch net-smc91x-fix-m68k-kernel-compilation-for-coldfire-cpu.patch +nilfs2-fix-unexpected-freezing-of-nilfs_segctor_sync.patch +nilfs2-fix-potential-hang-in-nilfs_detach_log_writer.patch tty-n_gsm-fix-possible-out-of-bounds-in-gsm0_receive.patch -- 2.39.5