ext4_inode_attach_jinode() publishes ei->jinode to concurrent users. It used to set ei->jinode before jbd2_journal_init_jbd_inode(), allowing a reader to observe a non-NULL jinode with i_vfs_inode still unset. The fast commit flush path can then pass this jinode to jbd2_wait_inode_data(), which dereferences i_vfs_inode->i_mapping and may crash. Below is the crash I observe: ``` BUG: unable to handle page fault for address: 000000010beb47f4 PGD 110e51067 P4D 110e51067 PUD 0 Oops: Oops: 0000 [#1] SMP NOPTI CPU: 1 UID: 0 PID: 4850 Comm: fc_fsync_bench_ Not tainted 6.18.0-00764-g795a690c06a5 #1 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.17.0-2-2 04/01/2014 RIP: 0010:xas_find_marked+0x3d/0x2e0 Code: e0 03 48 83 f8 02 0f 84 f0 01 00 00 48 8b 47 08 48 89 c3 48 39 c6 0f 82 fd 01 00 00 48 85 c9 74 3d 48 83 f9 03 77 63 4c 8b 0f <49> 8b 71 08 48 c7 47 18 00 00 00 00 48 89 f1 83 e1 03 48 83 f9 02 RSP: 0018:ffffbbee806e7bf0 EFLAGS: 00010246 RAX: 000000000010beb4 RBX: 000000000010beb4 RCX: 0000000000000003 RDX: 0000000000000001 RSI: 0000002000300000 RDI: ffffbbee806e7c10 RBP: 0000000000000001 R08: 0000002000300000 R09: 000000010beb47ec R10: ffff9ea494590090 R11: 0000000000000000 R12: 0000002000300000 R13: ffffbbee806e7c90 R14: ffff9ea494513788 R15: ffffbbee806e7c88 FS: 00007fc2f9e3e6c0(0000) GS:ffff9ea6b1444000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000010beb47f4 CR3: 0000000119ac5000 CR4: 0000000000750ef0 PKRU: 55555554 Call Trace: filemap_get_folios_tag+0x87/0x2a0 __filemap_fdatawait_range+0x5f/0xd0 ? srso_alias_return_thunk+0x5/0xfbef5 ? __schedule+0x3e7/0x10c0 ? srso_alias_return_thunk+0x5/0xfbef5 ? srso_alias_return_thunk+0x5/0xfbef5 ? srso_alias_return_thunk+0x5/0xfbef5 ? preempt_count_sub+0x5f/0x80 ? srso_alias_return_thunk+0x5/0xfbef5 ? cap_safe_nice+0x37/0x70 ? srso_alias_return_thunk+0x5/0xfbef5 ? preempt_count_sub+0x5f/0x80 ? srso_alias_return_thunk+0x5/0xfbef5 filemap_fdatawait_range_keep_errors+0x12/0x40 ext4_fc_commit+0x697/0x8b0 ? ext4_file_write_iter+0x64b/0x950 ? srso_alias_return_thunk+0x5/0xfbef5 ? preempt_count_sub+0x5f/0x80 ? srso_alias_return_thunk+0x5/0xfbef5 ? vfs_write+0x356/0x480 ? srso_alias_return_thunk+0x5/0xfbef5 ? preempt_count_sub+0x5f/0x80 ext4_sync_file+0xf7/0x370 do_fsync+0x3b/0x80 ? syscall_trace_enter+0x108/0x1d0 __x64_sys_fdatasync+0x16/0x20 do_syscall_64+0x62/0x2c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e ... ``` Fix this by initializing the jbd2_inode first. Use smp_wmb() and WRITE_ONCE() to publish ei->jinode after initialization. Readers use READ_ONCE() to fetch the pointer. Fixes: a361293f5fede ("jbd2: Fix oops in jbd2_journal_file_inode()") Cc: stable@vger.kernel.org Signed-off-by: Li Chen --- Changes since v1: - Publish EXT4_I(inode)->jinode with smp_wmb() + WRITE_ONCE(), and fetch it with READ_ONCE() (instead of smp_store_release()/smp_load_acquire()), as suggeted by Jan. fs/ext4/ext4_jbd2.h | 16 ++++++++++++---- fs/ext4/fast_commit.c | 7 +++++-- fs/ext4/inode.c | 15 +++++++++++---- fs/ext4/super.c | 11 +++++++---- 4 files changed, 35 insertions(+), 14 deletions(-) diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h index 63d17c5201b5..2d5343441b71 100644 --- a/fs/ext4/ext4_jbd2.h +++ b/fs/ext4/ext4_jbd2.h @@ -336,18 +336,26 @@ static inline int ext4_journal_force_commit(journal_t *journal) static inline int ext4_jbd2_inode_add_write(handle_t *handle, struct inode *inode, loff_t start_byte, loff_t length) { - if (ext4_handle_valid(handle)) + if (ext4_handle_valid(handle)) { + struct jbd2_inode *jinode; + + jinode = READ_ONCE(EXT4_I(inode)->jinode); return jbd2_journal_inode_ranged_write(handle, - EXT4_I(inode)->jinode, start_byte, length); + jinode, start_byte, length); + } return 0; } static inline int ext4_jbd2_inode_add_wait(handle_t *handle, struct inode *inode, loff_t start_byte, loff_t length) { - if (ext4_handle_valid(handle)) + if (ext4_handle_valid(handle)) { + struct jbd2_inode *jinode; + + jinode = READ_ONCE(EXT4_I(inode)->jinode); return jbd2_journal_inode_ranged_wait(handle, - EXT4_I(inode)->jinode, start_byte, length); + jinode, start_byte, length); + } return 0; } diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c index f575751f1cae..a80ed2d6df81 100644 --- a/fs/ext4/fast_commit.c +++ b/fs/ext4/fast_commit.c @@ -972,16 +972,19 @@ static int ext4_fc_flush_data(journal_t *journal) struct super_block *sb = journal->j_private; struct ext4_sb_info *sbi = EXT4_SB(sb); struct ext4_inode_info *ei; + struct jbd2_inode *jinode; int ret = 0; list_for_each_entry(ei, &sbi->s_fc_q[FC_Q_MAIN], i_fc_list) { - ret = jbd2_submit_inode_data(journal, ei->jinode); + jinode = READ_ONCE(ei->jinode); + ret = jbd2_submit_inode_data(journal, jinode); if (ret) return ret; } list_for_each_entry(ei, &sbi->s_fc_q[FC_Q_MAIN], i_fc_list) { - ret = jbd2_wait_inode_data(journal, ei->jinode); + jinode = READ_ONCE(ei->jinode); + ret = jbd2_wait_inode_data(journal, jinode); if (ret) return ret; } diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index da96db5f2345..d99296d7315f 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -128,6 +128,8 @@ void ext4_inode_csum_set(struct inode *inode, struct ext4_inode *raw, static inline int ext4_begin_ordered_truncate(struct inode *inode, loff_t new_size) { + struct jbd2_inode *jinode = READ_ONCE(EXT4_I(inode)->jinode); + trace_ext4_begin_ordered_truncate(inode, new_size); /* * If jinode is zero, then we never opened the file for @@ -135,10 +137,10 @@ static inline int ext4_begin_ordered_truncate(struct inode *inode, * jbd2_journal_begin_ordered_truncate() since there's no * outstanding writes we need to flush. */ - if (!EXT4_I(inode)->jinode) + if (!jinode) return 0; return jbd2_journal_begin_ordered_truncate(EXT4_JOURNAL(inode), - EXT4_I(inode)->jinode, + jinode, new_size); } @@ -4478,8 +4480,13 @@ int ext4_inode_attach_jinode(struct inode *inode) spin_unlock(&inode->i_lock); return -ENOMEM; } - ei->jinode = jinode; - jbd2_journal_init_jbd_inode(ei->jinode, inode); + jbd2_journal_init_jbd_inode(jinode, inode); + /* + * Publish ->jinode only after it is fully initialized so that + * readers never observe a partially initialized jbd2_inode. + */ + smp_wmb(); + WRITE_ONCE(ei->jinode, jinode); jinode = NULL; } spin_unlock(&inode->i_lock); diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 69eb63dde983..5cf6c2b54bbb 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -1526,17 +1526,20 @@ static void destroy_inodecache(void) void ext4_clear_inode(struct inode *inode) { + struct jbd2_inode *jinode; + ext4_fc_del(inode); invalidate_inode_buffers(inode); clear_inode(inode); ext4_discard_preallocations(inode); ext4_es_remove_extent(inode, 0, EXT_MAX_BLOCKS); dquot_drop(inode); - if (EXT4_I(inode)->jinode) { + jinode = READ_ONCE(EXT4_I(inode)->jinode); + if (jinode) { jbd2_journal_release_jbd_inode(EXT4_JOURNAL(inode), - EXT4_I(inode)->jinode); - jbd2_free_inode(EXT4_I(inode)->jinode); - EXT4_I(inode)->jinode = NULL; + jinode); + jbd2_free_inode(jinode); + WRITE_ONCE(EXT4_I(inode)->jinode, NULL); } fscrypt_put_encryption_info(inode); fsverity_cleanup_inode(inode); -- 2.52.0