[RFC PATCH 0/3] scsi: qedf: sanitise uaccess

[Oleksandr Natalenko <oleksandr@redhat.com>]

qedf driver, debugfs part of it specifically, touches __user pointers
directly for printing out info to userspace via sprintf(), which may
cause crash like this:

BUG: unable to handle kernel paging request at 00007ffd1d6b43a0
IP: [<ffffffffaa7a882a>] string.isra.7+0x6a/0xf0
Oops: 0003 [#1] SMP
Call Trace:
 [<ffffffffaa7a9f31>] vsnprintf+0x201/0x6a0
 [<ffffffffaa7aa556>] sprintf+0x56/0x80
 [<ffffffffc04227ed>] qedf_dbg_stop_io_on_error_cmd_read+0x6d/0x90 [qedf]
 [<ffffffffaa65bb2f>] vfs_read+0x9f/0x170
 [<ffffffffaa65cb82>] SyS_pread64+0x92/0xc0

Avoid this by preparing the info in a kernel buffer first, either
allocated on stack for small printouts, or via vmalloc() for big ones,
and then copying it to the userspace properly.

I'm not sure how big the vmalloc()'ed buffer should be, and also whether
vmalloc()'ing it directly in the _read() function is a good idea, hence
RFC prefix.

The qedf_dbg_stop_io_on_error_cmd_read()-related patch is actually tested,
the rest is compile-tested only.

Oleksandr Natalenko (3):
  scsi: qedf: do not touch __user pointer in
    qedf_dbg_stop_io_on_error_cmd_read() directly
  scsi: qedf: do not touch __user pointer in qedf_dbg_debug_cmd_read()
    directly
  scsi: qedf: do not touch __user pointer in qedf_dbg_fp_int_cmd_read()
    directly

 drivers/scsi/qedf/qedf_dbg.h     |  2 ++
 drivers/scsi/qedf/qedf_debugfs.c | 35 +++++++++++++++++++-------------
 2 files changed, 23 insertions(+), 14 deletions(-)

--
2.41.0