Bluetooth: hci_core: Prefer struct_size over open coded arithmetic

Commit Message

Erick Archer May 12, 2024, 2:17 p.m. UTC

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 hci_dev_list_req" and this
structure ends in a flexible array:

struct hci_dev_list_req {
	[...]
	struct hci_dev_req dev_req[];	/* hci_dev_req structures */
};

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 dr[n] instead of (dr + 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 <[e-mail]>
---
 include/net/bluetooth/hci_sock.h |  2 +-
 net/bluetooth/hci_core.c         | 15 ++++++---------
 2 files changed, 7 insertions(+), 10 deletions(-)

Comments

[e-mail] May 12, 2024, 2:56 p.m. UTC | #1

This is automated email and please do not reply to this email!

Dear submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
This is a CI test results with your patch series:
PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=852655

---Test result---

Test Summary:
CheckPatch                    PASS      0.78 seconds
GitLint                       FAIL      0.49 seconds
SubjectPrefix                 PASS      0.10 seconds
BuildKernel                   PASS      29.77 seconds
CheckAllWarning               PASS      32.45 seconds
CheckSparse                   PASS      39.05 seconds
CheckSmatch                   FAIL      34.54 seconds
BuildKernel32                 PASS      29.03 seconds
TestRunnerSetup               PASS      520.38 seconds
TestRunner_l2cap-tester       PASS      20.58 seconds
TestRunner_iso-tester         FAIL      33.47 seconds
TestRunner_bnep-tester        PASS      4.74 seconds
TestRunner_mgmt-tester        PASS      110.56 seconds
TestRunner_rfcomm-tester      PASS      7.28 seconds
TestRunner_sco-tester         PASS      15.00 seconds
TestRunner_ioctl-tester       PASS      7.65 seconds
TestRunner_mesh-tester        PASS      5.77 seconds
TestRunner_smp-tester         PASS      6.71 seconds
TestRunner_userchan-tester    PASS      4.87 seconds
IncrementalBuild              PASS      28.07 seconds

Details
##############################
Test: GitLint - FAIL
Desc: Run gitlint
Output:
Bluetooth: hci_core: Prefer struct_size over open coded arithmetic

WARNING: I3 - ignore-body-lines: gitlint will be switching from using Python regex 'match' (match beginning) to 'search' (match anywhere) semantics. Please review your ignore-body-lines.regex option accordingly. To remove this warning, set general.regex-style-search=True. More details: https://jorisroovers.github.io/gitlint/configuration/#regex-style-search
10: B3 Line contains hard tab characters (\t): "	[...]"
11: B3 Line contains hard tab characters (\t): "	struct hci_dev_req dev_req[];	/* hci_dev_req structures */"
37: B1 Line exceeds max length (117>80): "Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]"
##############################
Test: CheckSmatch - FAIL
Desc: Run smatch tool with source
Output:

Segmentation fault (core dumped)
make[4]: *** [scripts/Makefile.build:244: net/bluetooth/hci_core.o] Error 139
make[4]: *** Deleting file 'net/bluetooth/hci_core.o'
make[3]: *** [scripts/Makefile.build:485: net/bluetooth] Error 2
make[2]: *** [scripts/Makefile.build:485: net] Error 2
make[2]: *** Waiting for unfinished jobs....
Segmentation fault (core dumped)
make[4]: *** [scripts/Makefile.build:244: drivers/bluetooth/bcm203x.o] Error 139
make[4]: *** Deleting file 'drivers/bluetooth/bcm203x.o'
make[4]: *** Waiting for unfinished jobs....
make[3]: *** [scripts/Makefile.build:485: drivers/bluetooth] Error 2
make[2]: *** [scripts/Makefile.build:485: drivers] Error 2
make[1]: *** [/github/workspace/src/src/Makefile:1919: .] Error 2
make: *** [Makefile:240: __sub-make] Error 2
##############################
Test: TestRunner_iso-tester - FAIL
Desc: Run iso-tester with test-runner
Output:
Total: 122, Passed: 121 (99.2%), Failed: 1, Not Run: 0

Failed Test Cases
ISO Connect2 Suspend - Success                       Failed       4.230 seconds


---
Regards,
Linux Bluetooth

Kees Cook May 13, 2024, 3:08 a.m. UTC | #2

On Sun, May 12, 2024 at 04:17:06PM +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 hci_dev_list_req" and this
> structure ends in a flexible array:
> 
> struct hci_dev_list_req {
> 	[...]
> 	struct hci_dev_req dev_req[];	/* hci_dev_req structures */
> };
> 
> 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 dr[n] instead of (dr + 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 <[e-mail]>

Looks right to me. Thanks!

Reviewed-by: Kees Cook <[e-mail]>

Luiz Augusto von Dentz May 13, 2024, 4:31 p.m. UTC | #3

Hi Eric,

On Sun, May 12, 2024 at 11:08 PM Kees Cook <[e-mail]> wrote:
>
> On Sun, May 12, 2024 at 04:17:06PM +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 hci_dev_list_req" and this
> > structure ends in a flexible array:
> >
> > struct hci_dev_list_req {
> >       [...]
> >       struct hci_dev_req dev_req[];   /* hci_dev_req structures */
> > };
> >
> > 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 dr[n] instead of (dr + n).

Have the change above split on its own patch.

> > 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 <[e-mail]>
>
> Looks right to me. Thanks!
>
> Reviewed-by: Kees Cook <[e-mail]>
>
> --
> Kees Cook

Erick Archer May 13, 2024, 5:19 p.m. UTC | #4

Hi Kees and Luiz,
First of all, thanks for the reviews.

On Mon, May 13, 2024 at 12:31:29PM -0400, Luiz Augusto von Dentz wrote:
> Hi Eric,
> 
> On Sun, May 12, 2024 at 11:08 PM Kees Cook <[e-mail]> wrote:
> >
> > On Sun, May 12, 2024 at 04:17:06PM +0200, Erick Archer wrote:
> > > [...]
> > > Also remove the "size" variable as it is no longer needed and refactor
> > > the list_for_each_entry() loop to use dr[n] instead of (dr + n).
> 
> Have the change above split on its own patch.

Ok, no problem. I will send a new version.

Regards,
Erick

Patch

diff --git a/include/net/bluetooth/hci_sock.h b/include/net/bluetooth/hci_sock.h
index 9949870f7d78..13e8cd4414a1 100644
--- a/include/net/bluetooth/hci_sock.h
+++ b/include/net/bluetooth/hci_sock.h
@@ -144,7 +144,7 @@  struct hci_dev_req {
 
 struct hci_dev_list_req {
 	__u16  dev_num;
-	struct hci_dev_req dev_req[];	/* hci_dev_req structures */
+	struct hci_dev_req dev_req[] __counted_by(dev_num);
 };
 
 struct hci_conn_list_req {
diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index adfd53a9fcd4..cae8a67bcd62 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -837,7 +837,7 @@  int hci_get_dev_list(void __user *arg)
 	struct hci_dev *hdev;
 	struct hci_dev_list_req *dl;
 	struct hci_dev_req *dr;
-	int n = 0, size, err;
+	int n = 0, err;
 	__u16 dev_num;
 
 	if (get_user(dev_num, (__u16 __user *) arg))
@@ -846,12 +846,11 @@  int hci_get_dev_list(void __user *arg)
 	if (!dev_num || dev_num > (PAGE_SIZE * 2) / sizeof(*dr))
 		return -EINVAL;
 
-	size = sizeof(*dl) + dev_num * sizeof(*dr);
-
-	dl = kzalloc(size, GFP_KERNEL);
+	dl = kzalloc(struct_size(dl, dev_req, dev_num), GFP_KERNEL);
 	if (!dl)
 		return -ENOMEM;
 
+	dl->dev_num = dev_num;
 	dr = dl->dev_req;
 
 	read_lock(&hci_dev_list_lock);
@@ -865,8 +864,8 @@  int hci_get_dev_list(void __user *arg)
 		if (hci_dev_test_flag(hdev, HCI_AUTO_OFF))
 			flags &= ~BIT(HCI_UP);
 
-		(dr + n)->dev_id  = hdev->id;
-		(dr + n)->dev_opt = flags;
+		dr[n].dev_id  = hdev->id;
+		dr[n].dev_opt = flags;
 
 		if (++n >= dev_num)
 			break;
@@ -874,9 +873,7 @@  int hci_get_dev_list(void __user *arg)
 	read_unlock(&hci_dev_list_lock);
 
 	dl->dev_num = n;
-	size = sizeof(*dl) + n * sizeof(*dr);
-
-	err = copy_to_user(arg, dl, size);
+	err = copy_to_user(arg, dl, struct_size(dl, dev_req, n));
 	kfree(dl);
 
 	return err ? -EFAULT : 0;