[Ocfs2-devel] [PATCH] ocfs2: reduce ioctl stack usage

[Arnd Bergmann]

From: Arnd Bergmann <arnd at arndb.de>

On 32-bit architectures with KASAN_STACK enabled, the total stack usage
of the ocfs2_ioctl function grows beyond the warning limit:

fs/ocfs2/ioctl.c: In function 'ocfs2_ioctl':
fs/ocfs2/ioctl.c:934:1: error: the frame size of 1448 bytes is larger than 1400 bytes [-Werror=frame-larger-than=]

Move each of the variables into a basic block, and mark ocfs2_info_handle()
as noinline_for_stack, in order to have the variable share stack slots.

Signed-off-by: Arnd Bergmann <arnd at arndb.de>
---
 fs/ocfs2/ioctl.c | 37 ++++++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/fs/ocfs2/ioctl.c b/fs/ocfs2/ioctl.c
index 811a6ea374bb..b1550ba73f96 100644
--- a/fs/ocfs2/ioctl.c
+++ b/fs/ocfs2/ioctl.c
@@ -803,8 +803,8 @@ static int ocfs2_get_request_ptr(struct ocfs2_info *info, int idx,
  * a better backward&forward compatibility, since a small piece of
  * request will be less likely to be broken if disk layout get changed.
  */
-static int ocfs2_info_handle(struct inode *inode, struct ocfs2_info *info,
-			     int compat_flag)
+static noinline_for_stack int
+ocfs2_info_handle(struct inode *inode, struct ocfs2_info *info, int compat_flag)
 {
 	int i, status = 0;
 	u64 req_addr;
@@ -840,27 +840,26 @@ static int ocfs2_info_handle(struct inode *inode, struct ocfs2_info *info,
 long ocfs2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	struct inode *inode = file_inode(filp);
-	int new_clusters;
-	int status;
-	struct ocfs2_space_resv sr;
-	struct ocfs2_new_group_input input;
-	struct reflink_arguments args;
-	const char __user *old_path;
-	const char __user *new_path;
-	bool preserve;
-	struct ocfs2_info info;
 	void __user *argp = (void __user *)arg;
+	int status;
 
 	switch (cmd) {
 	case OCFS2_IOC_RESVSP:
 	case OCFS2_IOC_RESVSP64:
 	case OCFS2_IOC_UNRESVSP:
 	case OCFS2_IOC_UNRESVSP64:
+	{
+		struct ocfs2_space_resv sr;
+
 		if (copy_from_user(&sr, (int __user *) arg, sizeof(sr)))
 			return -EFAULT;
 
 		return ocfs2_change_file_space(filp, cmd, &sr);
+	}
 	case OCFS2_IOC_GROUP_EXTEND:
+	{
+		int new_clusters;
+
 		if (!capable(CAP_SYS_RESOURCE))
 			return -EPERM;
 
@@ -873,8 +872,12 @@ long ocfs2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		status = ocfs2_group_extend(inode, new_clusters);
 		mnt_drop_write_file(filp);
 		return status;
+	}
 	case OCFS2_IOC_GROUP_ADD:
 	case OCFS2_IOC_GROUP_ADD64:
+	{
+		struct ocfs2_new_group_input input;
+
 		if (!capable(CAP_SYS_RESOURCE))
 			return -EPERM;
 
@@ -887,7 +890,14 @@ long ocfs2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		status = ocfs2_group_add(inode, &input);
 		mnt_drop_write_file(filp);
 		return status;
+	}
 	case OCFS2_IOC_REFLINK:
+	{
+		struct reflink_arguments args;
+		const char __user *old_path;
+		const char __user *new_path;
+		bool preserve;
+
 		if (copy_from_user(&args, argp, sizeof(args)))
 			return -EFAULT;
 		old_path = (const char __user *)(unsigned long)args.old_path;
@@ -895,11 +905,16 @@ long ocfs2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		preserve = (args.preserve != 0);
 
 		return ocfs2_reflink_ioctl(inode, old_path, new_path, preserve);
+	}
 	case OCFS2_IOC_INFO:
+	{
+		struct ocfs2_info info;
+
 		if (copy_from_user(&info, argp, sizeof(struct ocfs2_info)))
 			return -EFAULT;
 
 		return ocfs2_info_handle(inode, &info, 0);
+	}
 	case FITRIM:
 	{
 		struct super_block *sb = inode->i_sb;
-- 
2.39.2