linux-kernel - Re: [RFC PATCH 0/3] scsi: qedf: sanitise uaccess

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Date:   Mon, 24 Jul 2023 09:03:32 -0400
From:   Laurence Oberman <loberman@...hat.com>
To:     Oleksandr Natalenko <oleksandr@...hat.com>,
        linux-kernel@...r.kernel.org
Cc:     linux-scsi@...r.kernel.org, Saurav Kashyap <skashyap@...vell.com>,
        Javed Hasan <jhasan@...vell.com>,
        GR-QLogic-Storage-Upstream@...vell.com,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Jozef Bacik <jobacik@...hat.com>, Rob Evers <revers@...hat.com>
Subject: Re: [RFC PATCH 0/3] scsi: qedf: sanitise uaccess

On Mon, 2023-07-24 at 14:02 +0200, Oleksandr Natalenko wrote:
> 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
> 

I will test the series, the one patch was already tested.
This was reproduced in our LAB
Will report back after testing

Regards
Laurence