From: Greg KH <gregkh@linuxfoundation.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Jason@zx2c4.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH v2] drivers: char: mem: Fix thinkos in kmem address checks
Date: Tue, 10 Jan 2017 18:49:14 +0100 [thread overview]
Message-ID: <20170110174914.GA27165@kroah.com> (raw)
In-Reply-To: <1b8da4cd537f5dd91ff28450c78df893e0ff1622.1483632724.git.robin.murphy@arm.com>
On Thu, Jan 05, 2017 at 05:15:01PM +0000, Robin Murphy wrote:
> When borrowing the pfn_valid() check from mmap_kmem(), somebody managed
> to get physical and virtual addresses spectacularly muddled up, such
> that we've ended up with checks for one being the other. Whilst this
> does indeed prevent out-of-bounds accesses crashing, on most systems
> it also prevents the more desirable use-case of working at all ever.
>
> Check the *virtual* offset correctly for what it is. Furthermore, do
> so in the right place - a read or write may span multiple pages, so a
> single up-front check is insufficient. High memory accesses already
> have a similar validity check just before the copy_to_user() call, so
> just make the low memory path fully consistent with that.
>
> Reported-by: Jason A. Donenfeld <Jason@zx2c4.com>
> CC: stable@vger.kernel.org
> Fixes: 148a1bc84398 ("drivers: char: mem: Check {read,write}_kmem() addresses")
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Jason, did this patch fix your issue?
thanks,
greg k-h
> ---
>
> Third time lucky... And if there's some other problem with this one then
> I guess we may as well just go ahead with Jason's revert, forget the whole
> thing, and let 'cat /dev/kmem' go back to crashing on non-x86 :)
>
> Robin.
>
> drivers/char/mem.c | 10 ++++------
> 1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/char/mem.c b/drivers/char/mem.c
> index 5bb1985ec484..6d9cc2d39d22 100644
> --- a/drivers/char/mem.c
> +++ b/drivers/char/mem.c
> @@ -381,9 +381,6 @@ static ssize_t read_kmem(struct file *file, char __user *buf,
> char *kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
> int err = 0;
>
> - if (!pfn_valid(PFN_DOWN(p)))
> - return -EIO;
> -
> read = 0;
> if (p < (unsigned long) high_memory) {
> low_count = count;
> @@ -412,6 +409,8 @@ static ssize_t read_kmem(struct file *file, char __user *buf,
> * by the kernel or data corruption may occur
> */
> kbuf = xlate_dev_kmem_ptr((void *)p);
> + if (!virt_addr_valid(kbuf))
> + return -ENXIO;
>
> if (copy_to_user(buf, kbuf, sz))
> return -EFAULT;
> @@ -482,6 +481,8 @@ static ssize_t do_write_kmem(unsigned long p, const char __user *buf,
> * corruption may occur.
> */
> ptr = xlate_dev_kmem_ptr((void *)p);
> + if (!virt_addr_valid(ptr))
> + return -ENXIO;
>
> copied = copy_from_user(ptr, buf, sz);
> if (copied) {
> @@ -512,9 +513,6 @@ static ssize_t write_kmem(struct file *file, const char __user *buf,
> char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
> int err = 0;
>
> - if (!pfn_valid(PFN_DOWN(p)))
> - return -EIO;
> -
> if (p < (unsigned long) high_memory) {
> unsigned long to_write = min_t(unsigned long, count,
> (unsigned long)high_memory - p);
> --
> 2.10.2.dirty
next prev parent reply other threads:[~2017-01-10 17:48 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-04 11:37 [PATCH] drivers: char: mem: Fix thinko in kmem address checks Robin Murphy
2017-01-04 11:45 ` Greg KH
2017-01-04 17:19 ` Greg KH
2017-01-04 16:46 ` kbuild test robot
2017-01-05 17:15 ` [PATCH v2] drivers: char: mem: Fix thinkos " Robin Murphy
2017-01-10 17:49 ` Greg KH [this message]
2017-01-11 19:18 ` Jason A. Donenfeld
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170110174914.GA27165@kroah.com \
--to=gregkh@linuxfoundation.org \
--cc=Jason@zx2c4.com \
--cc=linux-kernel@vger.kernel.org \
--cc=robin.murphy@arm.com \
--cc=stable@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).