fs/proc/kcore.c: Make bounce buffer global for read

Next patch adds bounce buffer for ktext area, so it's
convenient to have single bounce buffer for both
vmalloc/module and ktext cases.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 10 deletions

diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index a939f5ed7f89..bd3ac9dca252 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -430,6 +430,7 @@ static void elf_kcore_store_hdr(char *bufp, int nphdr, int dataoff)
 static ssize_t
 read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
 {
+        char *buf = file->private_data;
         ssize_t acc = 0;
         size_t size, tsz;
         size_t elf_buflen;
@@ -500,18 +501,10 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
                         if (clear_user(buffer, tsz))
                                 return -EFAULT;
                 } else if (is_vmalloc_or_module_addr((void *)start)) {
-                        char * elf_buf;
-
-                        elf_buf = kzalloc(tsz, GFP_KERNEL);
-                        if (!elf_buf)
-                                return -ENOMEM;
-                        vread(elf_buf, (char *)start, tsz);
+                        vread(buf, (char *)start, tsz);
                         /* we have to zero-fill user buffer even if no read */
-                        if (copy_to_user(buffer, elf_buf, tsz)) {
-                                kfree(elf_buf);
+                        if (copy_to_user(buffer, buf, tsz))
                                 return -EFAULT;
-                        }
-                        kfree(elf_buf);
                 } else {
                         if (kern_addr_valid(start)) {
                                 unsigned long n;
@@ -549,6 +542,11 @@ static int open_kcore(struct inode *inode, struct file *filp)
 {
         if (!capable(CAP_SYS_RAWIO))
                 return -EPERM;
+
+        filp->private_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
+        if (!filp->private_data)
+                return -ENOMEM;
+
         if (kcore_need_update)
                 kcore_update_ram();
         if (i_size_read(inode) != proc_root_kcore->size) {
@@ -559,10 +557,16 @@ static int open_kcore(struct inode *inode, struct file *filp)
         return 0;
 }
 
+static int release_kcore(struct inode *inode, struct file *file)
+{
+        kfree(file->private_data);
+        return 0;
+}
 
 static const struct file_operations proc_kcore_operations = {
         .read           = read_kcore,
         .open           = open_kcore,
+        .release        = release_kcore,
         .llseek         = default_llseek,
 };