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Date:   Fri, 29 Sep 2023 19:30:18 +0300
From:   Alexey Dobriyan <adobriyan@gmail.com>
To:     akpm@linux-foundation.org
Cc:     linux-kernel@vger.kernel.org
Subject: [PATCH] proc: use initializer for clearing some buffers
Message-ID: <3821d3a2-6e10-4629-b0d5-9519d828ab72@p183>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Precedence: bulk

Save LOC by using dark magic of initialisation instead of memset().

Those buffer aren't passed to userspace directly so padding is not
an issue.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

 fs/proc/base.c     |   16 ++++++----------
 fs/proc/task_mmu.c |   11 +++--------
 2 files changed, 9 insertions(+), 18 deletions(-)

--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1153,11 +1153,10 @@ static int __set_oom_adj(struct file *file, int oom_adj, bool legacy)
 static ssize_t oom_adj_write(struct file *file, const char __user *buf,
 			     size_t count, loff_t *ppos)
 {
-	char buffer[PROC_NUMBUF];
+	char buffer[PROC_NUMBUF] = {};
 	int oom_adj;
 	int err;
 
-	memset(buffer, 0, sizeof(buffer));
 	if (count > sizeof(buffer) - 1)
 		count = sizeof(buffer) - 1;
 	if (copy_from_user(buffer, buf, count)) {
@@ -1213,11 +1212,10 @@ static ssize_t oom_score_adj_read(struct file *file, char __user *buf,
 static ssize_t oom_score_adj_write(struct file *file, const char __user *buf,
 					size_t count, loff_t *ppos)
 {
-	char buffer[PROC_NUMBUF];
+	char buffer[PROC_NUMBUF] = {};
 	int oom_score_adj;
 	int err;
 
-	memset(buffer, 0, sizeof(buffer));
 	if (count > sizeof(buffer) - 1)
 		count = sizeof(buffer) - 1;
 	if (copy_from_user(buffer, buf, count)) {
@@ -1358,13 +1356,13 @@ static ssize_t proc_fault_inject_write(struct file * file,
 			const char __user * buf, size_t count, loff_t *ppos)
 {
 	struct task_struct *task;
-	char buffer[PROC_NUMBUF];
+	char buffer[PROC_NUMBUF] = {};
 	int make_it_fail;
 	int rv;
 
 	if (!capable(CAP_SYS_RESOURCE))
 		return -EPERM;
-	memset(buffer, 0, sizeof(buffer));
+
 	if (count > sizeof(buffer) - 1)
 		count = sizeof(buffer) - 1;
 	if (copy_from_user(buffer, buf, count))
@@ -1509,11 +1507,10 @@ sched_autogroup_write(struct file *file, const char __user *buf,
 {
 	struct inode *inode = file_inode(file);
 	struct task_struct *p;
-	char buffer[PROC_NUMBUF];
+	char buffer[PROC_NUMBUF] = {};
 	int nice;
 	int err;
 
-	memset(buffer, 0, sizeof(buffer));
 	if (count > sizeof(buffer) - 1)
 		count = sizeof(buffer) - 1;
 	if (copy_from_user(buffer, buf, count))
@@ -1666,10 +1663,9 @@ static ssize_t comm_write(struct file *file, const char __user *buf,
 {
 	struct inode *inode = file_inode(file);
 	struct task_struct *p;
-	char buffer[TASK_COMM_LEN];
+	char buffer[TASK_COMM_LEN] = {};
 	const size_t maxlen = sizeof(buffer) - 1;
 
-	memset(buffer, 0, sizeof(buffer));
 	if (copy_from_user(buffer, buf, count > maxlen ? maxlen : count))
 		return -EFAULT;
 
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -849,9 +849,7 @@ static void __show_smap(struct seq_file *m, const struct mem_size_stats *mss,
 static int show_smap(struct seq_file *m, void *v)
 {
 	struct vm_area_struct *vma = v;
-	struct mem_size_stats mss;
-
-	memset(&mss, 0, sizeof(mss));
+	struct mem_size_stats mss = {};
 
 	smap_gather_stats(vma, &mss, 0);
 
@@ -877,7 +875,7 @@ static int show_smap(struct seq_file *m, void *v)
 static int show_smaps_rollup(struct seq_file *m, void *v)
 {
 	struct proc_maps_private *priv = m->private;
-	struct mem_size_stats mss;
+	struct mem_size_stats mss = {};
 	struct mm_struct *mm = priv->mm;
 	struct vm_area_struct *vma;
 	unsigned long vma_start = 0, last_vma_end = 0;
@@ -893,8 +891,6 @@ static int show_smaps_rollup(struct seq_file *m, void *v)
 		goto out_put_task;
 	}
 
-	memset(&mss, 0, sizeof(mss));
-
 	ret = mmap_read_lock_killable(mm);
 	if (ret)
 		goto out_put_mm;
@@ -1246,14 +1242,13 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
 				size_t count, loff_t *ppos)
 {
 	struct task_struct *task;
-	char buffer[PROC_NUMBUF];
+	char buffer[PROC_NUMBUF] = {};
 	struct mm_struct *mm;
 	struct vm_area_struct *vma;
 	enum clear_refs_types type;
 	int itype;
 	int rv;
 
-	memset(buffer, 0, sizeof(buffer));
 	if (count > sizeof(buffer) - 1)
 		count = sizeof(buffer) - 1;
 	if (copy_from_user(buffer, buf, count))