From: Lizhi Xu lizhi.xu@windriver.com
[ Upstream commit 285cec318bf5a7a6c8ba999b2b6ec96f9a20590f ]
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@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=5d0bdc98770e6c55a0fd Signed-off-by: Lizhi Xu lizhi.xu@windriver.com Signed-off-by: Konstantin Komarov almaz.alexandrovich@paragon-software.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 3f96a11804c90..d3a31bad21f9d 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;