lkml.org 
[lkml]   [2021]   [Oct]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: WARNING in __kernel_read
On Wed, Oct 06, 2021 at 01:17:32PM +0100, Matthew Wilcox wrote:
> On Wed, Oct 06, 2021 at 05:33:47PM +0800, Hao Sun wrote:
> > C reproducer: https://drive.google.com/file/d/1RzAsyIZzw5X_m340nY9fu4KWjGdG98pv/view?usp=sharing
>
> It's easier than this reproducer makes it look.
>
> res = syscall(__NR_openat, -1, 0x20000080ul, 0x4c003ul, 0x10ul);
> syscall(__NR_finit_module, r[0], 0ul, 3ul);
>
> should be enough. Basically, userspace opens an fd without FMODE_READ
> and passes it to finit_module().
>
> > ------------[ cut here ]------------
> > WARNING: CPU: 1 PID: 28082 at fs/read_write.c:429
> > __kernel_read+0x3bb/0x410 fs/read_write.c:429
> > Modules linked in:
> > CPU: 1 PID: 28082 Comm: syz-executor Not tainted 5.15.0-rc3+ #21
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> > rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
> > RIP: 0010:__kernel_read+0x3bb/0x410 fs/read_write.c:429
> > Call Trace:
> > kernel_read+0x47/0x60 fs/read_write.c:461
> > kernel_read_file+0x20a/0x370 fs/kernel_read_file.c:93
> > kernel_read_file_from_fd+0x55/0x90 fs/kernel_read_file.c:184
> > __do_sys_finit_module+0x89/0x110 kernel/module.c:4180
>
> finit_module() is not the only caller of kernel_read_file_from_fd()
> which passes it a fd that userspace passed in, for example
> kexec_file_load() doesn't validate the fd either. We could validate
> the fd in individual syscalls, in kernel_read_file_from_fd()
> or just do what vfs_read() does and return -EBADF without warning.
>
> So, one of these two patches. Christoph, Al, what's your preference?

I think the warning was something Linux wanted. So the first one seems
like the way to go.

\
 
 \ /
  Last update: 2021-10-12 08:22    [W:0.058 / U:0.892 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site