Convert snd-page-alloc proc file to use seq_file (CVE-2007-4571)

changeset ccec6e2c in mainline.

Use seq_file for the proc file read/write of snd-page-alloc module.
This automatically fixes bugs in the old proc code.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

sound/core/memalloc.c

@@ -27,6 +27,7 @@
 #include <linux/pci.h>
 #include <linux/slab.h>
 #include <linux/mm.h>
+#include <linux/seq_file.h>
 #include <asm/uaccess.h>
 #include <linux/dma-mapping.h>
 #include <linux/moduleparam.h>
@@ -481,53 +482,54 @@ static void free_all_reserved_pages(void)
 #define SND_MEM_PROC_FILE	"driver/snd-page-alloc"
 static struct proc_dir_entry *snd_mem_proc;
 
-static int snd_mem_proc_read(char *page, char **start, off_t off,
-			     int count, int *eof, void *data)
+static int snd_mem_proc_read(struct seq_file *seq, void *offset)
 {
-	int len = 0;
 	long pages = snd_allocated_pages >> (PAGE_SHIFT-12);
 	struct snd_mem_list *mem;
 	int devno;
 	static char *types[] = { "UNKNOWN", "CONT", "DEV", "DEV-SG", "SBUS" };
 
 	mutex_lock(&list_mutex);
-	len += snprintf(page + len, count - len,
-			"pages  : %li bytes (%li pages per %likB)\n",
-			pages * PAGE_SIZE, pages, PAGE_SIZE / 1024);
+	seq_printf(seq, "pages  : %li bytes (%li pages per %likB)\n",
+		   pages * PAGE_SIZE, pages, PAGE_SIZE / 1024);
 	devno = 0;
 	list_for_each_entry(mem, &mem_list_head, list) {
 		devno++;
-		len += snprintf(page + len, count - len,
-				"buffer %d : ID %08x : type %s\n",
-				devno, mem->id, types[mem->buffer.dev.type]);
-		len += snprintf(page + len, count - len,
-				"  addr = 0x%lx, size = %d bytes\n",
-				(unsigned long)mem->buffer.addr, (int)mem->buffer.bytes);
+		seq_printf(seq, "buffer %d : ID %08x : type %s\n",
+			   devno, mem->id, types[mem->buffer.dev.type]);
+		seq_printf(seq, "  addr = 0x%lx, size = %d bytes\n",
+			   (unsigned long)mem->buffer.addr,
+			   (int)mem->buffer.bytes);
 	}
 	mutex_unlock(&list_mutex);
-	return len;
+	return 0;
+}
+
+static int snd_mem_proc_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, snd_mem_proc_read, NULL);
 }
 
 /* FIXME: for pci only - other bus? */
 #ifdef CONFIG_PCI
 #define gettoken(bufp) strsep(bufp, " \t\n")
 
-static int snd_mem_proc_write(struct file *file, const char __user *buffer,
-			      unsigned long count, void *data)
+static ssize_t snd_mem_proc_write(struct file *file, const char __user * buffer,
+				  size_t count, loff_t * ppos)
 {
 	char buf[128];
 	char *token, *p;
 
-	if (count > ARRAY_SIZE(buf) - 1)
-		count = ARRAY_SIZE(buf) - 1;
+	if (count > sizeof(buf) - 1)
+		return -EINVAL;
 	if (copy_from_user(buf, buffer, count))
 		return -EFAULT;
-	buf[ARRAY_SIZE(buf) - 1] = '\0';
+	buf[count] = '\0';
 
 	p = buf;
 	token = gettoken(&p);
 	if (! token || *token == '#')
-		return (int)count;
+		return count;
 	if (strcmp(token, "add") == 0) {
 		char *endp;
 		int vendor, device, size, buffers;
@@ -548,7 +550,7 @@ static int snd_mem_proc_write(struct file *file, const char __user *buffer,
 		    (buffers = simple_strtol(token, NULL, 0)) <= 0 ||
 		    buffers > 4) {
 			printk(KERN_ERR "snd-page-alloc: invalid proc write format\n");
-			return (int)count;
+			return count;
 		}
 		vendor &= 0xffff;
 		device &= 0xffff;
@@ -560,7 +562,7 @@ static int snd_mem_proc_write(struct file *file, const char __user *buffer,
 				if (pci_set_dma_mask(pci, mask) < 0 ||
 				    pci_set_consistent_dma_mask(pci, mask) < 0) {
 					printk(KERN_ERR "snd-page-alloc: cannot set DMA mask %lx for pci %04x:%04x\n", mask, vendor, device);
-					return (int)count;
+					return count;
 				}
 			}
 			for (i = 0; i < buffers; i++) {
@@ -570,7 +572,7 @@ static int snd_mem_proc_write(struct file *file, const char __user *buffer,
 							size, &dmab) < 0) {
 					printk(KERN_ERR "snd-page-alloc: cannot allocate buffer pages (size = %d)\n", size);
 					pci_dev_put(pci);
-					return (int)count;
+					return count;
 				}
 				snd_dma_reserve_buf(&dmab, snd_dma_pci_buf_id(pci));
 			}
@@ -596,9 +598,21 @@ static int snd_mem_proc_write(struct file *file, const char __user *buffer,
 		free_all_reserved_pages();
 	else
 		printk(KERN_ERR "snd-page-alloc: invalid proc cmd\n");
-	return (int)count;
+	return count;
 }
 #endif /* CONFIG_PCI */
+
+static const struct file_operations snd_mem_proc_fops = {
+	.owner		= THIS_MODULE,
+	.open		= snd_mem_proc_open,
+	.read		= seq_read,
+#ifdef CONFIG_PCI
+	.write		= snd_mem_proc_write,
+#endif
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
 #endif /* CONFIG_PROC_FS */
 
 /*
@@ -609,12 +623,8 @@ static int __init snd_mem_init(void)
 {
 #ifdef CONFIG_PROC_FS
 	snd_mem_proc = create_proc_entry(SND_MEM_PROC_FILE, 0644, NULL);
-	if (snd_mem_proc) {
-		snd_mem_proc->read_proc = snd_mem_proc_read;
-#ifdef CONFIG_PCI
-		snd_mem_proc->write_proc = snd_mem_proc_write;
-#endif
-	}
+	if (snd_mem_proc)
+		snd_mem_proc->proc_fops = &snd_mem_proc_fops;
 #endif
 	return 0;
 }