* [PATCH v2] tty: rfcomm: prefer struct_size over open coded arithmetic
@ 2024-05-12 11:17 Erick Archer
2024-05-13 3:03 ` Kees Cook
2024-05-13 5:07 ` Jiri Slaby
0 siblings, 2 replies; 6+ messages in thread
From: Erick Archer @ 2024-05-12 11:17 UTC (permalink / raw
To: Marcel Holtmann, Johan Hedberg, Luiz Augusto von Dentz,
David S. Miller, Eric Dumazet, Jakub Kicinski, Paolo Abeni,
Kees Cook, Gustavo A. R. Silva, Nathan Chancellor,
Nick Desaulniers, Bill Wendling, Justin Stitt, Jiri Slaby (SUSE),
Greg Kroah-Hartman, Geert Uytterhoeven
Cc: Erick Archer, linux-bluetooth, netdev, linux-kernel,
linux-hardening, llvm
This is an effort to get rid of all multiplications from allocation
functions in order to prevent integer overflows [1][2].
As the "dl" variable is a pointer to "struct rfcomm_dev_list_req" and
this structure ends in a flexible array:
struct rfcomm_dev_list_req {
[...]
struct rfcomm_dev_info dev_info[];
};
the preferred way in the kernel is to use the struct_size() helper to
do the arithmetic instead of the calculation "size + count * size" in
the kzalloc() and copy_to_user() functions.
At the same time, prepare for the coming implementation by GCC and Clang
of the __counted_by attribute. Flexible array members annotated with
__counted_by can have their accesses bounds-checked at run-time via
CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for
strcpy/memcpy-family functions).
In this case, it is important to note that the logic needs a little
refactoring to ensure that the "dev_num" member is initialized before
the first access to the flex array. Specifically, add the assignment
before the list_for_each_entry() loop.
Also remove the "size" variable as it is no longer needed and refactor
the list_for_each_entry() loop to use di[n] instead of (di + n).
This way, the code is more readable, idiomatic and safer.
This code was detected with the help of Coccinelle, and audited and
modified manually.
Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
Link: https://github.com/KSPP/linux/issues/160 [2]
Signed-off-by: Erick Archer <erick.archer@outlook.com>
---
Changes in v2:
- Add the __counted_by() attribute (Kees Cook).
- Refactor the list_for_each_entry() loop to use di[n] instead of
(di + n) (Kees Cook).
Previous versions:
v1 -> https://lore.kernel.org/linux-hardening/AS8PR02MB723725E0069F7AE8F64E876E8B142@AS8PR02MB7237.eurprd02.prod.outlook.com/
---
include/net/bluetooth/rfcomm.h | 2 +-
net/bluetooth/rfcomm/tty.c | 23 ++++++++++-------------
2 files changed, 11 insertions(+), 14 deletions(-)
diff --git a/include/net/bluetooth/rfcomm.h b/include/net/bluetooth/rfcomm.h
index 99d26879b02a..c05882476900 100644
--- a/include/net/bluetooth/rfcomm.h
+++ b/include/net/bluetooth/rfcomm.h
@@ -355,7 +355,7 @@ struct rfcomm_dev_info {
struct rfcomm_dev_list_req {
u16 dev_num;
- struct rfcomm_dev_info dev_info[];
+ struct rfcomm_dev_info dev_info[] __counted_by(dev_num);
};
int rfcomm_dev_ioctl(struct sock *sk, unsigned int cmd, void __user *arg);
diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index 69c75c041fe1..af80d599c337 100644
--- a/net/bluetooth/rfcomm/tty.c
+++ b/net/bluetooth/rfcomm/tty.c
@@ -504,7 +504,7 @@ static int rfcomm_get_dev_list(void __user *arg)
struct rfcomm_dev *dev;
struct rfcomm_dev_list_req *dl;
struct rfcomm_dev_info *di;
- int n = 0, size, err;
+ int n = 0, err;
u16 dev_num;
BT_DBG("");
@@ -515,12 +515,11 @@ static int rfcomm_get_dev_list(void __user *arg)
if (!dev_num || dev_num > (PAGE_SIZE * 4) / sizeof(*di))
return -EINVAL;
- size = sizeof(*dl) + dev_num * sizeof(*di);
-
- dl = kzalloc(size, GFP_KERNEL);
+ dl = kzalloc(struct_size(dl, dev_info, dev_num), GFP_KERNEL);
if (!dl)
return -ENOMEM;
+ dl->dev_num = dev_num;
di = dl->dev_info;
mutex_lock(&rfcomm_dev_lock);
@@ -528,12 +527,12 @@ static int rfcomm_get_dev_list(void __user *arg)
list_for_each_entry(dev, &rfcomm_dev_list, list) {
if (!tty_port_get(&dev->port))
continue;
- (di + n)->id = dev->id;
- (di + n)->flags = dev->flags;
- (di + n)->state = dev->dlc->state;
- (di + n)->channel = dev->channel;
- bacpy(&(di + n)->src, &dev->src);
- bacpy(&(di + n)->dst, &dev->dst);
+ di[n].id = dev->id;
+ di[n].flags = dev->flags;
+ di[n].state = dev->dlc->state;
+ di[n].channel = dev->channel;
+ bacpy(&di[n].src, &dev->src);
+ bacpy(&di[n].dst, &dev->dst);
tty_port_put(&dev->port);
if (++n >= dev_num)
break;
@@ -542,9 +541,7 @@ static int rfcomm_get_dev_list(void __user *arg)
mutex_unlock(&rfcomm_dev_lock);
dl->dev_num = n;
- size = sizeof(*dl) + n * sizeof(*di);
-
- err = copy_to_user(arg, dl, size);
+ err = copy_to_user(arg, dl, struct_size(dl, dev_info, n));
kfree(dl);
return err ? -EFAULT : 0;
--
2.25.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH v2] tty: rfcomm: prefer struct_size over open coded arithmetic
2024-05-12 11:17 [PATCH v2] tty: rfcomm: prefer struct_size over open coded arithmetic Erick Archer
@ 2024-05-13 3:03 ` Kees Cook
2024-05-13 5:07 ` Jiri Slaby
1 sibling, 0 replies; 6+ messages in thread
From: Kees Cook @ 2024-05-13 3:03 UTC (permalink / raw
To: Erick Archer
Cc: Marcel Holtmann, Johan Hedberg, Luiz Augusto von Dentz,
David S. Miller, Eric Dumazet, Jakub Kicinski, Paolo Abeni,
Gustavo A. R. Silva, Nathan Chancellor, Nick Desaulniers,
Bill Wendling, Justin Stitt, Jiri Slaby (SUSE),
Greg Kroah-Hartman, Geert Uytterhoeven, linux-bluetooth, netdev,
linux-kernel, linux-hardening, llvm
On Sun, May 12, 2024 at 01:17:24PM +0200, Erick Archer wrote:
> This is an effort to get rid of all multiplications from allocation
> functions in order to prevent integer overflows [1][2].
>
> As the "dl" variable is a pointer to "struct rfcomm_dev_list_req" and
> this structure ends in a flexible array:
>
> struct rfcomm_dev_list_req {
> [...]
> struct rfcomm_dev_info dev_info[];
> };
>
> the preferred way in the kernel is to use the struct_size() helper to
> do the arithmetic instead of the calculation "size + count * size" in
> the kzalloc() and copy_to_user() functions.
>
> At the same time, prepare for the coming implementation by GCC and Clang
> of the __counted_by attribute. Flexible array members annotated with
> __counted_by can have their accesses bounds-checked at run-time via
> CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for
> strcpy/memcpy-family functions).
>
> In this case, it is important to note that the logic needs a little
> refactoring to ensure that the "dev_num" member is initialized before
> the first access to the flex array. Specifically, add the assignment
> before the list_for_each_entry() loop.
>
> Also remove the "size" variable as it is no longer needed and refactor
> the list_for_each_entry() loop to use di[n] instead of (di + n).
>
> This way, the code is more readable, idiomatic and safer.
>
> This code was detected with the help of Coccinelle, and audited and
> modified manually.
>
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
> Link: https://github.com/KSPP/linux/issues/160 [2]
> Signed-off-by: Erick Archer <erick.archer@outlook.com>
Looks good!
Reviewed-by: Kees Cook <keescook@chromium.org>
> [...]
> - bacpy(&(di + n)->src, &dev->src);
> - bacpy(&(di + n)->dst, &dev->dst);
> + bacpy(&di[n].src, &dev->src);
> + bacpy(&di[n].dst, &dev->dst);
Not an issue with your patch, but this helper is really pointless in the
Bluetooth tree:
static inline void bacpy(bdaddr_t *dst, const bdaddr_t *src)
{
memcpy(dst, src, sizeof(bdaddr_t));
}
So the above could just be:
di[n].src = dev->src;
di[n].dst = dev->dst;
:P
-Kees
--
Kees Cook
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH v2] tty: rfcomm: prefer struct_size over open coded arithmetic
2024-05-12 11:17 [PATCH v2] tty: rfcomm: prefer struct_size over open coded arithmetic Erick Archer
2024-05-13 3:03 ` Kees Cook
@ 2024-05-13 5:07 ` Jiri Slaby
2024-05-13 16:29 ` Luiz Augusto von Dentz
1 sibling, 1 reply; 6+ messages in thread
From: Jiri Slaby @ 2024-05-13 5:07 UTC (permalink / raw
To: Erick Archer, Marcel Holtmann, Johan Hedberg,
Luiz Augusto von Dentz, David S. Miller, Eric Dumazet,
Jakub Kicinski, Paolo Abeni, Kees Cook, Gustavo A. R. Silva,
Nathan Chancellor, Nick Desaulniers, Bill Wendling, Justin Stitt,
Greg Kroah-Hartman, Geert Uytterhoeven
Cc: linux-bluetooth, netdev, linux-kernel, linux-hardening, llvm
On 12. 05. 24, 13:17, Erick Archer wrote:
> This is an effort to get rid of all multiplications from allocation
> functions in order to prevent integer overflows [1][2].
>
> As the "dl" variable is a pointer to "struct rfcomm_dev_list_req" and
> this structure ends in a flexible array:
...
> --- a/include/net/bluetooth/rfcomm.h
> +++ b/include/net/bluetooth/rfcomm.h
...
> @@ -528,12 +527,12 @@ static int rfcomm_get_dev_list(void __user *arg)
> list_for_each_entry(dev, &rfcomm_dev_list, list) {
> if (!tty_port_get(&dev->port))
> continue;
> - (di + n)->id = dev->id;
> - (di + n)->flags = dev->flags;
> - (di + n)->state = dev->dlc->state;
> - (di + n)->channel = dev->channel;
> - bacpy(&(di + n)->src, &dev->src);
> - bacpy(&(di + n)->dst, &dev->dst);
> + di[n].id = dev->id;
> + di[n].flags = dev->flags;
> + di[n].state = dev->dlc->state;
> + di[n].channel = dev->channel;
> + bacpy(&di[n].src, &dev->src);
> + bacpy(&di[n].dst, &dev->dst);
This does not relate much to "prefer struct_size over open coded
arithmetic". It should have been in a separate patch.
Other than that, LGTM.
thanks,
--
js
suse labs
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH v2] tty: rfcomm: prefer struct_size over open coded arithmetic
2024-05-13 5:07 ` Jiri Slaby
@ 2024-05-13 16:29 ` Luiz Augusto von Dentz
2024-05-13 17:12 ` Erick Archer
0 siblings, 1 reply; 6+ messages in thread
From: Luiz Augusto von Dentz @ 2024-05-13 16:29 UTC (permalink / raw
To: Jiri Slaby
Cc: Erick Archer, Marcel Holtmann, Johan Hedberg, David S. Miller,
Eric Dumazet, Jakub Kicinski, Paolo Abeni, Kees Cook,
Gustavo A. R. Silva, Nathan Chancellor, Nick Desaulniers,
Bill Wendling, Justin Stitt, Greg Kroah-Hartman,
Geert Uytterhoeven, linux-bluetooth, netdev, linux-kernel,
linux-hardening, llvm
Hi Jiri, Eric,
On Mon, May 13, 2024 at 1:07 AM Jiri Slaby <jirislaby@kernel.org> wrote:
>
> On 12. 05. 24, 13:17, Erick Archer wrote:
> > This is an effort to get rid of all multiplications from allocation
> > functions in order to prevent integer overflows [1][2].
> >
> > As the "dl" variable is a pointer to "struct rfcomm_dev_list_req" and
> > this structure ends in a flexible array:
> ...
> > --- a/include/net/bluetooth/rfcomm.h
> > +++ b/include/net/bluetooth/rfcomm.h
> ...
> > @@ -528,12 +527,12 @@ static int rfcomm_get_dev_list(void __user *arg)
> > list_for_each_entry(dev, &rfcomm_dev_list, list) {
> > if (!tty_port_get(&dev->port))
> > continue;
> > - (di + n)->id = dev->id;
> > - (di + n)->flags = dev->flags;
> > - (di + n)->state = dev->dlc->state;
> > - (di + n)->channel = dev->channel;
> > - bacpy(&(di + n)->src, &dev->src);
> > - bacpy(&(di + n)->dst, &dev->dst);
> > + di[n].id = dev->id;
> > + di[n].flags = dev->flags;
> > + di[n].state = dev->dlc->state;
> > + di[n].channel = dev->channel;
> > + bacpy(&di[n].src, &dev->src);
> > + bacpy(&di[n].dst, &dev->dst);
>
> This does not relate much to "prefer struct_size over open coded
> arithmetic". It should have been in a separate patch.
+1, please split these changes into its own patch so we can apply it separately.
> Other than that, LGTM.
>
> thanks,
> --
> js
> suse labs
>
--
Luiz Augusto von Dentz
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH v2] tty: rfcomm: prefer struct_size over open coded arithmetic
2024-05-13 16:29 ` Luiz Augusto von Dentz
@ 2024-05-13 17:12 ` Erick Archer
2024-05-13 18:51 ` Kees Cook
0 siblings, 1 reply; 6+ messages in thread
From: Erick Archer @ 2024-05-13 17:12 UTC (permalink / raw
To: Kees Cook, Jiri Slaby, Luiz Augusto von Dentz
Cc: Erick Archer, Marcel Holtmann, Johan Hedberg, David S. Miller,
Eric Dumazet, Jakub Kicinski, Paolo Abeni, Gustavo A. R. Silva,
Nathan Chancellor, Nick Desaulniers, Bill Wendling, Justin Stitt,
Greg Kroah-Hartman, Geert Uytterhoeven, linux-bluetooth, netdev,
linux-kernel, linux-hardening, llvm
Hi Kees, Jiri and Luiz,
First of all, thanks for the reviews.
On Mon, May 13, 2024 at 12:29:04PM -0400, Luiz Augusto von Dentz wrote:
> Hi Jiri, Eric,
>
> On Mon, May 13, 2024 at 1:07 AM Jiri Slaby <jirislaby@kernel.org> wrote:
> >
> > On 12. 05. 24, 13:17, Erick Archer wrote:
> > > This is an effort to get rid of all multiplications from allocation
> > > functions in order to prevent integer overflows [1][2].
> > >
> > > As the "dl" variable is a pointer to "struct rfcomm_dev_list_req" and
> > > this structure ends in a flexible array:
> > ...
> > > --- a/include/net/bluetooth/rfcomm.h
> > > +++ b/include/net/bluetooth/rfcomm.h
> > ...
> > > @@ -528,12 +527,12 @@ static int rfcomm_get_dev_list(void __user *arg)
> > > list_for_each_entry(dev, &rfcomm_dev_list, list) {
> > > if (!tty_port_get(&dev->port))
> > > continue;
> > > - (di + n)->id = dev->id;
> > > - (di + n)->flags = dev->flags;
> > > - (di + n)->state = dev->dlc->state;
> > > - (di + n)->channel = dev->channel;
> > > - bacpy(&(di + n)->src, &dev->src);
> > > - bacpy(&(di + n)->dst, &dev->dst);
> > > + di[n].id = dev->id;
> > > + di[n].flags = dev->flags;
> > > + di[n].state = dev->dlc->state;
> > > + di[n].channel = dev->channel;
> > > + bacpy(&di[n].src, &dev->src);
> > > + bacpy(&di[n].dst, &dev->dst);
> >
> > This does not relate much to "prefer struct_size over open coded
> > arithmetic". It should have been in a separate patch.
>
> +1, please split these changes into its own patch so we can apply it separately.
Ok, no problem. Also, I will simplify the "bacpy" lines with direct
assignments as Kees suggested:
di[n].src = dev->src;
di[n].dst = dev->dst;
instead of:
bacpy(&di[n].src, &dev->src);
bacpy(&di[n].dst, &dev->dst);
Regards,
Erick
> > Other than that, LGTM.
> >
> > thanks,
> > --
> > js
> > suse labs
> >
>
>
> --
> Luiz Augusto von Dentz
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH v2] tty: rfcomm: prefer struct_size over open coded arithmetic
2024-05-13 17:12 ` Erick Archer
@ 2024-05-13 18:51 ` Kees Cook
0 siblings, 0 replies; 6+ messages in thread
From: Kees Cook @ 2024-05-13 18:51 UTC (permalink / raw
To: Erick Archer
Cc: Jiri Slaby, Luiz Augusto von Dentz, Marcel Holtmann,
Johan Hedberg, David S. Miller, Eric Dumazet, Jakub Kicinski,
Paolo Abeni, Gustavo A. R. Silva, Nathan Chancellor,
Nick Desaulniers, Bill Wendling, Justin Stitt, Greg Kroah-Hartman,
Geert Uytterhoeven, linux-bluetooth, netdev, linux-kernel,
linux-hardening, llvm
On Mon, May 13, 2024 at 07:12:57PM +0200, Erick Archer wrote:
> Hi Kees, Jiri and Luiz,
> First of all, thanks for the reviews.
>
> On Mon, May 13, 2024 at 12:29:04PM -0400, Luiz Augusto von Dentz wrote:
> > Hi Jiri, Eric,
> >
> > On Mon, May 13, 2024 at 1:07 AM Jiri Slaby <jirislaby@kernel.org> wrote:
> > >
> > > On 12. 05. 24, 13:17, Erick Archer wrote:
> > > > This is an effort to get rid of all multiplications from allocation
> > > > functions in order to prevent integer overflows [1][2].
> > > >
> > > > As the "dl" variable is a pointer to "struct rfcomm_dev_list_req" and
> > > > this structure ends in a flexible array:
> > > ...
> > > > --- a/include/net/bluetooth/rfcomm.h
> > > > +++ b/include/net/bluetooth/rfcomm.h
> > > ...
> > > > @@ -528,12 +527,12 @@ static int rfcomm_get_dev_list(void __user *arg)
> > > > list_for_each_entry(dev, &rfcomm_dev_list, list) {
> > > > if (!tty_port_get(&dev->port))
> > > > continue;
> > > > - (di + n)->id = dev->id;
> > > > - (di + n)->flags = dev->flags;
> > > > - (di + n)->state = dev->dlc->state;
> > > > - (di + n)->channel = dev->channel;
> > > > - bacpy(&(di + n)->src, &dev->src);
> > > > - bacpy(&(di + n)->dst, &dev->dst);
> > > > + di[n].id = dev->id;
> > > > + di[n].flags = dev->flags;
> > > > + di[n].state = dev->dlc->state;
> > > > + di[n].channel = dev->channel;
> > > > + bacpy(&di[n].src, &dev->src);
> > > > + bacpy(&di[n].dst, &dev->dst);
> > >
> > > This does not relate much to "prefer struct_size over open coded
> > > arithmetic". It should have been in a separate patch.
> >
> > +1, please split these changes into its own patch so we can apply it separately.
>
> Ok, no problem. Also, I will simplify the "bacpy" lines with direct
> assignments as Kees suggested:
>
> di[n].src = dev->src;
> di[n].dst = dev->dst;
>
> instead of:
>
> bacpy(&di[n].src, &dev->src);
> bacpy(&di[n].dst, &dev->dst);
I think that's a separate thing and you can leave bacpy() as-is for now.
--
Kees Cook
^ permalink raw reply [flat|nested] 6+ messages in thread
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2024-05-12 11:17 [PATCH v2] tty: rfcomm: prefer struct_size over open coded arithmetic Erick Archer
2024-05-13 3:03 ` Kees Cook
2024-05-13 5:07 ` Jiri Slaby
2024-05-13 16:29 ` Luiz Augusto von Dentz
2024-05-13 17:12 ` Erick Archer
2024-05-13 18:51 ` Kees Cook
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