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Message-ID: <20241230071003.130590-1-lizhi.xu@windriver.com>
Date: Mon, 30 Dec 2024 15:10:03 +0800
From: Lizhi Xu <lizhi.xu@...driver.com>
To: <lizhi.xu@...driver.com>
CC: <almaz.alexandrovich@...agon-software.com>, <linux-kernel@...r.kernel.org>,
<ntfs3@...ts.linux.dev>,
<syzbot+5d0bdc98770e6c55a0fd@...kaller.appspotmail.com>,
<syzkaller-bugs@...glegroups.com>
Subject: [PATCH V2] fs/ntfs3: Keep write operations atomic
syzbot reported a NULL pointer dereference in __generic_file_write_iter. [1]
Before the write operation is completed, the user executes ioctl[2] to clear
the compress flag of the file, which causes the is_compressed() judgment to
return 0, further causing the program to enter the wrong process and call the
wrong ops ntfs_aops_cmpr, which triggers the null pointer dereference of
write_begin.
Use inode lock to synchronize ioctl and write to avoid this case.
[1]
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
Mem abort info:
ESR = 0x0000000086000006
EC = 0x21: IABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x06: level 2 translation fault
user pgtable: 4k pages, 48-bit VAs, pgdp=000000011896d000
[0000000000000000] pgd=0800000118b44403, p4d=0800000118b44403, pud=0800000117517403, pmd=0000000000000000
Internal error: Oops: 0000000086000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 UID: 0 PID: 6427 Comm: syz-executor347 Not tainted 6.13.0-rc3-syzkaller-g573067a5a685 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : 0x0
lr : generic_perform_write+0x29c/0x868 mm/filemap.c:4055
sp : ffff80009d4978a0
x29: ffff80009d4979c0 x28: dfff800000000000 x27: ffff80009d497bc8
x26: 0000000000000000 x25: ffff80009d497960 x24: ffff80008ba71c68
x23: 0000000000000000 x22: ffff0000c655dac0 x21: 0000000000001000
x20: 000000000000000c x19: 1ffff00013a92f2c x18: ffff0000e183aa1c
x17: 0004060000000014 x16: ffff800083275834 x15: 0000000000000001
x14: 0000000000000000 x13: 0000000000000001 x12: ffff0000c655dac0
x11: 0000000000ff0100 x10: 0000000000ff0100 x9 : 0000000000000000
x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
x5 : ffff80009d497980 x4 : ffff80009d497960 x3 : 0000000000001000
x2 : 0000000000000000 x1 : ffff0000e183a928 x0 : ffff0000d60b0fc0
Call trace:
0x0 (P)
__generic_file_write_iter+0xfc/0x204 mm/filemap.c:4156
ntfs_file_write_iter+0x54c/0x630 fs/ntfs3/file.c:1267
new_sync_write fs/read_write.c:586 [inline]
vfs_write+0x920/0xcf4 fs/read_write.c:679
ksys_write+0x15c/0x26c fs/read_write.c:731
__do_sys_write fs/read_write.c:742 [inline]
__se_sys_write fs/read_write.c:739 [inline]
__arm64_sys_write+0x7c/0x90 fs/read_write.c:739
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:744
el0t_64_sync_handler+0x84/0x108 arch/arm64/kernel/entry-common.c:762
[2]
ioctl$FS_IOC_SETFLAGS(r0, 0x40086602, &(0x7f00000000c0)=0x20)
Reported-by: syzbot+5d0bdc98770e6c55a0fd@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=5d0bdc98770e6c55a0fd
Signed-off-by: Lizhi Xu <lizhi.xu@...driver.com>
---
V1 -> V2: unlock and return err
fs/ntfs3/file.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
diff --git a/fs/ntfs3/file.c b/fs/ntfs3/file.c
index 3f96a11804c9..d3a31bad21f9 100644
--- a/fs/ntfs3/file.c
+++ b/fs/ntfs3/file.c
@@ -1228,21 +1228,22 @@ static ssize_t ntfs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
ssize_t ret;
int err;
- err = check_write_restriction(inode);
- if (err)
- return err;
-
- if (is_compressed(ni) && (iocb->ki_flags & IOCB_DIRECT)) {
- ntfs_inode_warn(inode, "direct i/o + compressed not supported");
- return -EOPNOTSUPP;
- }
-
if (!inode_trylock(inode)) {
if (iocb->ki_flags & IOCB_NOWAIT)
return -EAGAIN;
inode_lock(inode);
}
+ ret = check_write_restriction(inode);
+ if (ret)
+ goto out;
+
+ if (is_compressed(ni) && (iocb->ki_flags & IOCB_DIRECT)) {
+ ntfs_inode_warn(inode, "direct i/o + compressed not supported");
+ ret = -EOPNOTSUPP;
+ goto out;
+ }
+
ret = generic_write_checks(iocb, from);
if (ret <= 0)
goto out;
--
2.43.0
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