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[31.0.3.137]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a751561bb1bsm347310066b.37.2024.07.03.00.01.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Jul 2024 00:01:23 -0700 (PDT) From: =?UTF-8?q?Wojciech=20G=C5=82adysz?= To: syzbot+18df508cf00a0598d9a6@syzkaller.appspotmail.com Cc: adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, tytso@mit.edu, =?UTF-8?q?Wojciech=20G=C5=82adysz?= Subject: [PATCH] kernel/ext4: sanity check for NULL pointer after ext4_force_shutdown Date: Wed, 3 Jul 2024 09:01:12 +0200 Message-Id: <20240703070112.10235-1-wojciech.gladysz@infogain.com> X-Mailer: git-send-email 2.35.3 In-Reply-To: <000000000000f19a1406109eb5c5@google.com> References: <000000000000f19a1406109eb5c5@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Test case: 2 threads write short inline data to a file. In ext4_page_mkwrite the resulting inline data is converted. Handling ext4_grp_locked_error with description "block bitmap and bg descriptor inconsistent: X vs Y free clusters" calls ext4_force_shutdown. The conversion clears EXT4_STATE_MAY_INLINE_DATA but fails for ext4_destroy_inline_data_nolock and ext4_mark_iloc_dirty due to ext4_forced_shutdown. The restoration of inline data fails for the same reason not setting EXT4_STATE_MAY_INLINE_DATA. Without the flag set a regular process path in ext4_da_write_end follows trying to dereference page folio private pointer that has not been set. The fix calls early return with -EIO error shall the pointer to private be NULL. Sample crash report: Unable to handle kernel paging request at virtual address dfff800000000004 KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027] Mem abort info: ESR =3D 0x0000000096000005 EC =3D 0x25: DABT (current EL), IL =3D 32 bits SET =3D 0, FnV =3D 0 EA =3D 0, S1PTW =3D 0 FSC =3D 0x05: level 1 translation fault Data abort info: ISV =3D 0, ISS =3D 0x00000005, ISS2 =3D 0x00000000 CM =3D 0, WnR =3D 0, TnD =3D 0, TagAccess =3D 0 GCS =3D 0, Overlay =3D 0, DirtyBit =3D 0, Xs =3D 0 [dfff800000000004] address between user and kernel address ranges Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP Modules linked in: CPU: 1 PID: 20274 Comm: syz-executor185 Not tainted 6.9.0-rc7-syzkaller-gfd= a5695d692c #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Goo= gle 03/27/2024 pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=3D--) pc : __block_commit_write+0x64/0x2b0 fs/buffer.c:2167 lr : __block_commit_write+0x3c/0x2b0 fs/buffer.c:2160 sp : ffff8000a1957600 x29: ffff8000a1957610 x28: dfff800000000000 x27: ffff0000e30e34b0 x26: 0000000000000000 x25: dfff800000000000 x24: dfff800000000000 x23: fffffdffc397c9e0 x22: 0000000000000020 x21: 0000000000000020 x20: 0000000000000040 x19: fffffdffc397c9c0 x18: 1fffe000367bd196 x17: ffff80008eead000 x16: ffff80008ae89e3c x15: 00000000200000c0 x14: 1fffe0001cbe4e04 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000001 x10: 0000000000ff0100 x9 : 0000000000000000 x8 : 0000000000000004 x7 : 0000000000000000 x6 : 0000000000000000 x5 : fffffdffc397c9c0 x4 : 0000000000000020 x3 : 0000000000000020 x2 : 0000000000000040 x1 : 0000000000000020 x0 : fffffdffc397c9c0 Call trace: __block_commit_write+0x64/0x2b0 fs/buffer.c:2167 block_write_end+0xb4/0x104 fs/buffer.c:2253 ext4_da_do_write_end fs/ext4/inode.c:2955 [inline] ext4_da_write_end+0x2c4/0xa40 fs/ext4/inode.c:3028 generic_perform_write+0x394/0x588 mm/filemap.c:3985 ext4_buffered_write_iter+0x2c0/0x4ec fs/ext4/file.c:299 ext4_file_write_iter+0x188/0x1780 call_write_iter include/linux/fs.h:2110 [inline] new_sync_write fs/read_write.c:497 [inline] vfs_write+0x968/0xc3c fs/read_write.c:590 ksys_write+0x15c/0x26c fs/read_write.c:643 __do_sys_write fs/read_write.c:655 [inline] __se_sys_write fs/read_write.c:652 [inline] __arm64_sys_write+0x7c/0x90 fs/read_write.c:652 __invoke_syscall arch/arm64/kernel/syscall.c:34 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:48 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:133 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:152 el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712 el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598 Code: 97f85911 f94002da 91008356 d343fec8 (38796908) Reported-by: syzbot+18df508cf00a0598d9a6@syzkaller.appspotmail.com ---[ end trace 0000000000000000 ]--- ---------------- Code disassembly (best guess): 0: 97f85911 bl 0xffffffffffe16444 4: f94002da ldr x26, [x22] 8: 91008356 add x22, x26, #0x20 c: d343fec8 lsr x8, x22, #3 * 10: 38796908 ldrb w8, [x8, x25] <-- trapping instruction Reported-by: syzbot+18df508cf00a0598d9a6@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D18df508cf00a0598d9a6 Link: https://lore.kernel.org/all/000000000000f19a1406109eb5c5@google.com/T/ Signed-off-by: Wojciech G=C5=82adysz --- fs/buffer.c | 5 ++++- fs/ext4/inode.c | 5 +++++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/fs/buffer.c b/fs/buffer.c index 8c19e705b9c3..0d87d1f037e6 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -2186,7 +2186,10 @@ static void __block_commit_write(struct folio *folio= , size_t from, size_t to) unsigned blocksize; struct buffer_head *bh, *head; =20 - bh =3D head =3D folio_buffers(folio); + head =3D folio_buffers(folio); + if (!head) + return; + bh =3D head; blocksize =3D bh->b_size; =20 block_start =3D 0; diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 4bae9ccf5fe0..f14e77c4a6de 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2945,6 +2945,11 @@ static int ext4_da_do_write_end(struct address_space= *mapping, bool disksize_changed =3D false; loff_t new_i_size; =20 + if (unlikely(!folio_buffers(folio))) { + folio_unlock(folio); + folio_put(folio); + return -EIO; + } /* * block_write_end() will mark the inode as dirty with I_DIRTY_PAGES * flag, which all that's needed to trigger page writeback. --=20 2.35.3