* [PATCH v3 1/2] tty: rfcomm: prefer struct_size over open coded arithmetic
[not found] <20240517172150.5476-1-erick.archer@outlook.com>
@ 2024-05-17 17:21 ` Erick Archer
2024-05-17 17:56 ` tty: rfcomm: refactor rfcomm_get_dev_list() function bluez.test.bot
2024-05-17 17:21 ` [PATCH v3 2/2] tty: rfcomm: prefer array indexing over pointer arithmetic Erick Archer
1 sibling, 1 reply; 3+ messages in thread
From: Erick Archer @ 2024-05-17 17:21 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.
This way, the code is more readable 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]
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Erick Archer <erick.archer@outlook.com>
---
include/net/bluetooth/rfcomm.h | 2 +-
net/bluetooth/rfcomm/tty.c | 11 ++++-------
2 files changed, 5 insertions(+), 8 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..44b781e7569e 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);
@@ -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] 3+ messages in thread* [PATCH v3 2/2] tty: rfcomm: prefer array indexing over pointer arithmetic
[not found] <20240517172150.5476-1-erick.archer@outlook.com>
2024-05-17 17:21 ` [PATCH v3 1/2] tty: rfcomm: prefer struct_size over open coded arithmetic Erick Archer
@ 2024-05-17 17:21 ` Erick Archer
1 sibling, 0 replies; 3+ messages in thread
From: Erick Archer @ 2024-05-17 17:21 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
Refactor the list_for_each_entry() loop of rfcomm_get_dev_list()
function to use array indexing instead of pointer arithmetic.
This way, the code is more readable and idiomatic.
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Erick Archer <erick.archer@outlook.com>
---
net/bluetooth/rfcomm/tty.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index 44b781e7569e..af80d599c337 100644
--- a/net/bluetooth/rfcomm/tty.c
+++ b/net/bluetooth/rfcomm/tty.c
@@ -527,12 +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;
--
2.25.1
^ permalink raw reply related [flat|nested] 3+ messages in thread