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([2001:41d0:303:db6b::]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48a822bf3ffsm431044285e9.7.2026.05.05.05.33.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 May 2026 05:33:32 -0700 (PDT) From: Tristan Madani To: Dave Kleikamp Cc: jfs-discussion@lists.sourceforge.net, linux-kernel@vger.kernel.org, syzbot+c244f4a09ca85dd2ebc1@syzkaller.appspotmail.com, syzbot+885a4f3281b8d99c48d8@syzkaller.appspotmail.com, stable@vger.kernel.org, Tristan Madani Subject: [PATCH v2 2/2] jfs: wait for in-flight log I/O before freeing lbufs in lbmLogShutdown Date: Tue, 5 May 2026 12:33:30 +0000 Message-ID: <20260505123330.2822833-3-tristmd@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260505123330.2822833-1-tristmd@gmail.com> References: <20260501110236.43226-1-tristmd@gmail.com> <20260505123330.2822833-1-tristmd@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Tristan Madani lbmLogShutdown() frees log buffer (lbuf) pages and structures from log->lbuf_free. However, BIO completions (lbmIODone) may still be executing in softirq context when lbmLogShutdown() runs, because lbmIODone accesses lbuf fields (l_flag, l_log, l_freelist) before returning the buffer to the freelist. If lbmLogShutdown() runs concurrently with lbmIODone in-flight, it can free an lbuf that lbmIODone is still accessing -- resulting in a use-after-free. Fix this by adding an atomic io_count to struct jfs_log that tracks in-flight BIO operations. lbmStartIO increments it before submit_bio (or before calling lbmIODone directly for no_integrity mode), and lbmIODone decrements it after all lbuf accesses are complete. lbmLogShutdown waits for io_count to reach zero before freeing any lbufs. Reported-by: syzbot+c244f4a09ca85dd2ebc1@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=c244f4a09ca85dd2ebc1 Reported-by: syzbot+885a4f3281b8d99c48d8@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=885a4f3281b8d99c48d8 Fixes: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Tristan Madani --- fs/jfs/jfs_logmgr.c | 12 ++++++++++++ fs/jfs/jfs_logmgr.h | 2 ++ 2 files changed, 14 insertions(+) diff --git a/fs/jfs/jfs_logmgr.c b/fs/jfs/jfs_logmgr.c index 306165e61438c..95e95f71ec0fa 100644 --- a/fs/jfs/jfs_logmgr.c +++ b/fs/jfs/jfs_logmgr.c @@ -1804,6 +1804,8 @@ static int lbmLogInit(struct jfs_log * log) * avoid deadlock here. */ init_waitqueue_head(&log->free_wait); + atomic_set(&log->io_count, 0); + init_waitqueue_head(&log->io_done_wait); log->lbuf_free = NULL; @@ -1855,6 +1857,9 @@ static void lbmLogShutdown(struct jfs_log * log) jfs_info("lbmLogShutdown: log:0x%p", log); + /* Wait for all in-flight log I/O to complete */ + wait_event(log->io_done_wait, !atomic_read(&log->io_count)); + lbuf = log->lbuf_free; while (lbuf) { struct lbuf *next = lbuf->l_freelist; @@ -1976,6 +1981,8 @@ static int lbmRead(struct jfs_log * log, int pn, struct lbuf ** bpp) bio->bi_end_io = lbmIODone; bio->bi_private = bp; + + atomic_inc(&log->io_count); /*check if journaling to disk has been disabled*/ if (log->no_integrity) { bio->bi_iter.bi_size = 0; @@ -2123,6 +2130,8 @@ static void lbmStartIO(struct lbuf * bp) bio->bi_end_io = lbmIODone; bio->bi_private = bp; + atomic_inc(&log->io_count); + /* check if journaling to disk has been disabled */ if (log->no_integrity) { bio->bi_iter.bi_size = 0; @@ -2299,6 +2308,9 @@ static void lbmIODone(struct bio *bio) out: bp->l_flag |= lbmDONE; LCACHE_UNLOCK(flags); + + if (atomic_dec_and_test(&bp->l_log->io_count)) + wake_up(&bp->l_log->io_done_wait); } int jfsIOWait(void *arg) diff --git a/fs/jfs/jfs_logmgr.h b/fs/jfs/jfs_logmgr.h index 09e0ef6aeccef..cbf38ed27c950 100644 --- a/fs/jfs/jfs_logmgr.h +++ b/fs/jfs/jfs_logmgr.h @@ -367,6 +367,8 @@ struct jfs_log { struct lbuf *lbuf_free; /* 4: free lbufs */ wait_queue_head_t free_wait; /* 4: */ + atomic_t io_count; /* in-flight log I/O count */ + wait_queue_head_t io_done_wait; /* wait for io_count == 0 */ /* log write */ int logtid; /* 4: log tid */ -- 2.47.3