From cf4dfe3cad39cbd6309acbd514a7e07e6d15c356 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Tue, 22 Nov 2022 13:41:16 +0100 Subject: [PATCH] 4.9-stable patches added patches: nilfs2-fix-use-after-free-bug-of-ns_writer-on-remount.patch --- ...ter-free-bug-of-ns_writer-on-remount.patch | 118 ++++++++++++++++++ queue-4.9/series | 1 + 2 files changed, 119 insertions(+) create mode 100644 queue-4.9/nilfs2-fix-use-after-free-bug-of-ns_writer-on-remount.patch diff --git a/queue-4.9/nilfs2-fix-use-after-free-bug-of-ns_writer-on-remount.patch b/queue-4.9/nilfs2-fix-use-after-free-bug-of-ns_writer-on-remount.patch new file mode 100644 index 00000000000..1f859a9746d --- /dev/null +++ b/queue-4.9/nilfs2-fix-use-after-free-bug-of-ns_writer-on-remount.patch @@ -0,0 +1,118 @@ +From 8cccf05fe857a18ee26e20d11a8455a73ffd4efd Mon Sep 17 00:00:00 2001 +From: Ryusuke Konishi +Date: Fri, 4 Nov 2022 23:29:59 +0900 +Subject: nilfs2: fix use-after-free bug of ns_writer on remount + +From: Ryusuke Konishi + +commit 8cccf05fe857a18ee26e20d11a8455a73ffd4efd upstream. + +If a nilfs2 filesystem is downgraded to read-only due to metadata +corruption on disk and is remounted read/write, or if emergency read-only +remount is performed, detaching a log writer and synchronizing the +filesystem can be done at the same time. + +In these cases, use-after-free of the log writer (hereinafter +nilfs->ns_writer) can happen as shown in the scenario below: + + Task1 Task2 + -------------------------------- ------------------------------ + nilfs_construct_segment + nilfs_segctor_sync + init_wait + init_waitqueue_entry + add_wait_queue + schedule + nilfs_remount (R/W remount case) + nilfs_attach_log_writer + nilfs_detach_log_writer + nilfs_segctor_destroy + kfree + finish_wait + _raw_spin_lock_irqsave + __raw_spin_lock_irqsave + do_raw_spin_lock + debug_spin_lock_before <-- use-after-free + +While Task1 is sleeping, nilfs->ns_writer is freed by Task2. After Task1 +waked up, Task1 accesses nilfs->ns_writer which is already freed. This +scenario diagram is based on the Shigeru Yoshida's post [1]. + +This patch fixes the issue by not detaching nilfs->ns_writer on remount so +that this UAF race doesn't happen. Along with this change, this patch +also inserts a few necessary read-only checks with superblock instance +where only the ns_writer pointer was used to check if the filesystem is +read-only. + +Link: https://syzkaller.appspot.com/bug?id=79a4c002e960419ca173d55e863bd09e8112df8b +Link: https://lkml.kernel.org/r/20221103141759.1836312-1-syoshida@redhat.com [1] +Link: https://lkml.kernel.org/r/20221104142959.28296-1-konishi.ryusuke@gmail.com +Signed-off-by: Ryusuke Konishi +Reported-by: syzbot+f816fa82f8783f7a02bb@syzkaller.appspotmail.com +Reported-by: Shigeru Yoshida +Tested-by: Ryusuke Konishi +Cc: +Signed-off-by: Andrew Morton +Signed-off-by: Greg Kroah-Hartman +--- + fs/nilfs2/segment.c | 15 ++++++++------- + fs/nilfs2/super.c | 2 -- + 2 files changed, 8 insertions(+), 9 deletions(-) + +--- a/fs/nilfs2/segment.c ++++ b/fs/nilfs2/segment.c +@@ -329,7 +329,7 @@ void nilfs_relax_pressure_in_lock(struct + struct the_nilfs *nilfs = sb->s_fs_info; + struct nilfs_sc_info *sci = nilfs->ns_writer; + +- if (!sci || !sci->sc_flush_request) ++ if (sb->s_flags & MS_RDONLY || unlikely(!sci) || !sci->sc_flush_request) + return; + + set_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags); +@@ -2252,7 +2252,7 @@ int nilfs_construct_segment(struct super + struct nilfs_transaction_info *ti; + int err; + +- if (!sci) ++ if (sb->s_flags & MS_RDONLY || unlikely(!sci)) + return -EROFS; + + /* A call inside transactions causes a deadlock. */ +@@ -2291,7 +2291,7 @@ int nilfs_construct_dsync_segment(struct + struct nilfs_transaction_info ti; + int err = 0; + +- if (!sci) ++ if (sb->s_flags & MS_RDONLY || unlikely(!sci)) + return -EROFS; + + nilfs_transaction_lock(sb, &ti, 0); +@@ -2788,11 +2788,12 @@ int nilfs_attach_log_writer(struct super + + if (nilfs->ns_writer) { + /* +- * This happens if the filesystem was remounted +- * read/write after nilfs_error degenerated it into a +- * read-only mount. ++ * This happens if the filesystem is made read-only by ++ * __nilfs_error or nilfs_remount and then remounted ++ * read/write. In these cases, reuse the existing ++ * writer. + */ +- nilfs_detach_log_writer(sb); ++ return 0; + } + + nilfs->ns_writer = nilfs_segctor_new(sb, root); +--- a/fs/nilfs2/super.c ++++ b/fs/nilfs2/super.c +@@ -1147,8 +1147,6 @@ static int nilfs_remount(struct super_bl + if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY)) + goto out; + if (*flags & MS_RDONLY) { +- /* Shutting down log writer */ +- nilfs_detach_log_writer(sb); + sb->s_flags |= MS_RDONLY; + + /* diff --git a/queue-4.9/series b/queue-4.9/series index 27019a2b4a6..1b1fc867361 100644 --- a/queue-4.9/series +++ b/queue-4.9/series @@ -62,3 +62,4 @@ serial-8250-fall-back-to-non-dma-rx-if-iir_rdi-occurs.patch serial-8250_lpss-configure-dma-also-w-o-dma-filter.patch mmc-core-properly-select-voltage-range-without-power-cycle.patch misc-vmw_vmci-fix-an-infoleak-in-vmci_host_do_receive_datagram.patch +nilfs2-fix-use-after-free-bug-of-ns_writer-on-remount.patch -- 2.47.3