* [PATCH] drivers: char: mem: Fix thinko in kmem address checks
@ 2017-01-04 11:37 Robin Murphy
2017-01-04 11:45 ` Greg KH
` (2 more replies)
0 siblings, 3 replies; 7+ messages in thread
From: Robin Murphy @ 2017-01-04 11:37 UTC (permalink / raw)
To: gregkh, Jason; +Cc: linux-kernel, stable
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.
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>
---
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) {
--
2.10.2.dirty
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] drivers: char: mem: Fix thinko in kmem address checks
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
2 siblings, 1 reply; 7+ messages in thread
From: Greg KH @ 2017-01-04 11:45 UTC (permalink / raw)
To: Robin Murphy; +Cc: Jason, linux-kernel, stable
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@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>
> ---
> 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
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] drivers: char: mem: Fix thinko in kmem address checks
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 16:46 ` kbuild test robot
2017-01-05 17:15 ` [PATCH v2] drivers: char: mem: Fix thinkos " Robin Murphy
2 siblings, 0 replies; 7+ messages in thread
From: kbuild test robot @ 2017-01-04 16:46 UTC (permalink / raw)
To: Robin Murphy; +Cc: kbuild-all, gregkh, Jason, linux-kernel, stable
[-- Attachment #1: Type: text/plain, Size: 2299 bytes --]
Hi Robin,
[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on v4.10-rc2 next-20170104]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Robin-Murphy/drivers-char-mem-Fix-thinko-in-kmem-address-checks/20170104-235754
config: tile-allmodconfig (attached as .config)
compiler: tilegx-linux-gcc (GCC) 4.6.2
reproduce:
wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
make.cross ARCH=tile
All warnings (new ones prefixed by >>):
drivers/char/mem.c: In function 'read_kmem':
>> drivers/char/mem.c:384:2: warning: passing argument 1 of 'kaddr_to_pfn' makes pointer from integer without a cast [enabled by default]
arch/tile/include/asm/page.h:281:29: note: expected 'const volatile void *' but argument is of type 'long unsigned int'
drivers/char/mem.c: In function 'write_kmem':
drivers/char/mem.c:515:2: warning: passing argument 1 of 'kaddr_to_pfn' makes pointer from integer without a cast [enabled by default]
arch/tile/include/asm/page.h:281:29: note: expected 'const volatile void *' but argument is of type 'long unsigned int'
vim +/kaddr_to_pfn +384 drivers/char/mem.c
368
369 vma->vm_pgoff = pfn;
370 return mmap_mem(file, vma);
371 }
372
373 /*
374 * This function reads the *virtual* memory as seen by the kernel.
375 */
376 static ssize_t read_kmem(struct file *file, char __user *buf,
377 size_t count, loff_t *ppos)
378 {
379 unsigned long p = *ppos;
380 ssize_t low_count, read, sz;
381 char *kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
382 int err = 0;
383
> 384 if (!virt_addr_valid(p))
385 return -EIO;
386
387 read = 0;
388 if (p < (unsigned long) high_memory) {
389 low_count = count;
390 if (count > (unsigned long)high_memory - p)
391 low_count = (unsigned long)high_memory - p;
392
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 47087 bytes --]
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] drivers: char: mem: Fix thinko in kmem address checks
2017-01-04 11:45 ` Greg KH
@ 2017-01-04 17:19 ` Greg KH
0 siblings, 0 replies; 7+ messages in thread
From: Greg KH @ 2017-01-04 17:19 UTC (permalink / raw)
To: Robin Murphy; +Cc: Jason, linux-kernel, stable
On Wed, Jan 04, 2017 at 12:45:32PM +0100, Greg KH wrote:
> 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@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>
> > ---
> > 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?
Well, it fails kbuild testing, so can you try it again?
thanks,
greg k-h
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v2] drivers: char: mem: Fix thinkos in kmem address checks
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 16:46 ` kbuild test robot
@ 2017-01-05 17:15 ` Robin Murphy
2017-01-10 17:49 ` Greg KH
2 siblings, 1 reply; 7+ messages in thread
From: Robin Murphy @ 2017-01-05 17:15 UTC (permalink / raw)
To: gregkh, Jason; +Cc: linux-kernel, stable
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>
---
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
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH v2] drivers: char: mem: Fix thinkos in kmem address checks
2017-01-05 17:15 ` [PATCH v2] drivers: char: mem: Fix thinkos " Robin Murphy
@ 2017-01-10 17:49 ` Greg KH
2017-01-11 19:18 ` Jason A. Donenfeld
0 siblings, 1 reply; 7+ messages in thread
From: Greg KH @ 2017-01-10 17:49 UTC (permalink / raw)
To: Robin Murphy; +Cc: Jason, linux-kernel, stable
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
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2] drivers: char: mem: Fix thinkos in kmem address checks
2017-01-10 17:49 ` Greg KH
@ 2017-01-11 19:18 ` Jason A. Donenfeld
0 siblings, 0 replies; 7+ messages in thread
From: Jason A. Donenfeld @ 2017-01-11 19:18 UTC (permalink / raw)
To: Greg KH; +Cc: Robin Murphy, LKML, stable
Tested-by: Jason A. Donenfeld <Jason@zx2c4.com>
My extract-keys [1] utility works again:
$ sudo ./extract-keys wg0
0x08d3c7a3 IbbC5O9g2dTZBeLQoivmKZtdSGqufU+M2s2oaFzMfYA=
0xdf917af6 3cUm2mXNaZVzWDmJIZ9XlPpvJ63GH1uyUwKLN1g1Dhs=
[1] https://git.zx2c4.com/WireGuard/tree/contrib/examples/extract-keys
^ permalink raw reply [flat|nested] 7+ messages in thread
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2017-01-04 11:37 [PATCH] drivers: char: mem: Fix thinko in kmem address checks Robin Murphy
2017-01-04 11:45 ` Greg KH
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2017-01-04 16:46 ` kbuild test robot
2017-01-05 17:15 ` [PATCH v2] drivers: char: mem: Fix thinkos " Robin Murphy
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2017-01-11 19:18 ` Jason A. Donenfeld
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