On Wed, Jan 04, 2017 at 11:37:49AM +0000, Robin Murphy wrote:
> When borrowing the pfn_valid() check from mmap_kmem(), somebody managed
"sombody"? :)
> 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.
>
> Reported-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
> CC: stable@xxxxxxxxxxxxxxx
> Fixes: 148a1bc84398 ("drivers: char: mem: Check {read,write}_kmem() addresses")
> Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
> ---
> drivers/char/mem.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/char/mem.c b/drivers/char/mem.c
> index 5bb1985ec484..bdc6a4018604 100644
> --- a/drivers/char/mem.c
> +++ b/drivers/char/mem.c
> @@ -381,7 +381,7 @@ 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)))
> + if (!virt_addr_valid(p))
> return -EIO;
>
> read = 0;
> @@ -512,7 +512,7 @@ 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)))
> + if (!virt_addr_valid(p))
> return -EIO;
>
> if (p < (unsigned long) high_memory) {
Jason, can you verify this fixes your test case?
thanks,
greg k-h
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