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Subject[PATCH] dm/raid1: Remove VLA usage
On the quest to remove all VLAs from the kernel[1], this avoids VLAs
in dm-raid1.c by just using the maximum size for the stack arrays.
The nr_mirrors value was already capped at 9, so this makes it a trivial
adjustment to the array sizes.

[1] https://lkml.org/lkml/2018/3/7/621

Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/md/dm-raid1.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index 580c49cc8079..5903e492bb34 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -23,6 +23,8 @@

#define MAX_RECOVERY 1 /* Maximum number of regions recovered in parallel. */

+#define MAX_NR_MIRRORS (DM_KCOPYD_MAX_REGIONS + 1)
+
#define DM_RAID1_HANDLE_ERRORS 0x01
#define DM_RAID1_KEEP_LOG 0x02
#define errors_handled(p) ((p)->features & DM_RAID1_HANDLE_ERRORS)
@@ -255,7 +257,7 @@ static int mirror_flush(struct dm_target *ti)
unsigned long error_bits;

unsigned int i;
- struct dm_io_region io[ms->nr_mirrors];
+ struct dm_io_region io[MAX_NR_MIRRORS];
struct mirror *m;
struct dm_io_request io_req = {
.bi_op = REQ_OP_WRITE,
@@ -651,7 +653,7 @@ static void write_callback(unsigned long error, void *context)
static void do_write(struct mirror_set *ms, struct bio *bio)
{
unsigned int i;
- struct dm_io_region io[ms->nr_mirrors], *dest = io;
+ struct dm_io_region io[MAX_NR_MIRRORS], *dest = io;
struct mirror *m;
struct dm_io_request io_req = {
.bi_op = REQ_OP_WRITE,
@@ -1083,7 +1085,7 @@ static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
argc -= args_used;

if (!argc || sscanf(argv[0], "%u%c", &nr_mirrors, &dummy) != 1 ||
- nr_mirrors < 2 || nr_mirrors > DM_KCOPYD_MAX_REGIONS + 1) {
+ nr_mirrors < 2 || nr_mirrors > MAX_NR_MIRRORS) {
ti->error = "Invalid number of mirrors";
dm_dirty_log_destroy(dl);
return -EINVAL;
@@ -1404,7 +1406,7 @@ static void mirror_status(struct dm_target *ti, status_type_t type,
int num_feature_args = 0;
struct mirror_set *ms = (struct mirror_set *) ti->private;
struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
- char buffer[ms->nr_mirrors + 1];
+ char buffer[MAX_NR_MIRRORS + 1];

switch (type) {
case STATUSTYPE_INFO:
--
2.7.4

--
Kees Cook
Pixel Security

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