[PATCH] btrfs: allocate btrfs_ioctl_defrag_range_args on stack

[Maximilian Heyne]

From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>

commit c853a5783ebe123847886d432354931874367292 upstream.

Instead of using kmalloc() to allocate btrfs_ioctl_defrag_range_args,
allocate btrfs_ioctl_defrag_range_args on stack, the size is reasonably
small and ioctls are called in process context.

sizeof(btrfs_ioctl_defrag_range_args) = 48

Reviewed-by: Anand Jain <anand.jain@xxxxxxxxxx>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
CC: stable@xxxxxxxxxxxxxxx # 4.14+
[ This patch is needed to fix a memory leak of "range" that was
introduced when commit 173431b274a9 ("btrfs: defrag: reject unknown
flags of btrfs_ioctl_defrag_range_args") was backported to kernels
lacking this patch. Now with these two patches applied in reverse order,
range->flags needed to change back to range.flags.
This bug was discovered and resolved using Coverity Static Analysis
Security Testing (SAST) by Synopsys, Inc.]
Signed-off-by: Maximilian Heyne <mheyne@xxxxxxxxx>
---
 fs/btrfs/ioctl.c | 25 ++++++++-----------------
 1 file changed, 8 insertions(+), 17 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 049b837934e5..ab8ed187746e 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3148,7 +3148,7 @@ static int btrfs_ioctl_defrag(struct file *file, void __user *argp)
 {
 	struct inode *inode = file_inode(file);
 	struct btrfs_root *root = BTRFS_I(inode)->root;
-	struct btrfs_ioctl_defrag_range_args *range;
+	struct btrfs_ioctl_defrag_range_args range = {0};
 	int ret;
 
 	ret = mnt_want_write_file(file);
@@ -3180,37 +3180,28 @@ static int btrfs_ioctl_defrag(struct file *file, void __user *argp)
 			goto out;
 		}
 
-		range = kzalloc(sizeof(*range), GFP_KERNEL);
-		if (!range) {
-			ret = -ENOMEM;
-			goto out;
-		}
-
 		if (argp) {
-			if (copy_from_user(range, argp,
-					   sizeof(*range))) {
+			if (copy_from_user(&range, argp, sizeof(range))) {
 				ret = -EFAULT;
-				kfree(range);
 				goto out;
 			}
-			if (range->flags & ~BTRFS_DEFRAG_RANGE_FLAGS_SUPP) {
+			if (range.flags & ~BTRFS_DEFRAG_RANGE_FLAGS_SUPP) {
 				ret = -EOPNOTSUPP;
 				goto out;
 			}
 			/* compression requires us to start the IO */
-			if ((range->flags & BTRFS_DEFRAG_RANGE_COMPRESS)) {
-				range->flags |= BTRFS_DEFRAG_RANGE_START_IO;
-				range->extent_thresh = (u32)-1;
+			if ((range.flags & BTRFS_DEFRAG_RANGE_COMPRESS)) {
+				range.flags |= BTRFS_DEFRAG_RANGE_START_IO;
+				range.extent_thresh = (u32)-1;
 			}
 		} else {
 			/* the rest are all set to zero by kzalloc */
-			range->len = (u64)-1;
+			range.len = (u64)-1;
 		}
 		ret = btrfs_defrag_file(file_inode(file), file,
-					range, BTRFS_OLDEST_GENERATION, 0);
+					&range, BTRFS_OLDEST_GENERATION, 0);
 		if (ret > 0)
 			ret = 0;
-		kfree(range);
 		break;
 	default:
 		ret = -EINVAL;
-- 
2.40.1




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