Hello

I have found a race in core dumping. In binfmt_aout.c, binfmt_elf.c and
binfmt_aout32.c file->f_op->write is called without lock and so more
processes can get to VFS write function. This is the patch. I hope it
fixes the race. (but I can't reproduce it).

Mikulas

--- linux/fs/binfmt_aout.c.or	Mon May 10 15:21:05 1999
+++ linux/fs/binfmt_aout.c	Mon May 10 15:28:40 1999
@@ -58,8 +58,19 @@
  * These are the only things you should do on a core-file: use only these
  * macros to write out all the necessary info.
  */
-#define DUMP_WRITE(addr,nr) \
-while (file->f_op->write(file,(char *)(addr),(nr),&file->f_pos) != (nr)) goto close_coredump
+
+static int dump_write(struct file *file, const void *addr, int nr)
+{
+	int r;
+	down(&file->f_dentry->d_inode->i_sem);
+	r = file->f_op->write(file, addr, nr, &file->f_pos) == nr;
+	up(&file->f_dentry->d_inode->i_sem);
+	return r;
+}
+
+#define DUMP_WRITE(addr, nr)	\
+	if (!dump_write(file, (void *)(addr), (nr))) \
+		goto close_coredump;
 
 #define DUMP_SEEK(offset) \
 if (file->f_op->llseek) { \
--- linux/fs/binfmt_elf.c.or	Mon May 10 15:21:14 1999
+++ linux/fs/binfmt_elf.c	Mon May 10 15:28:28 1999
@@ -927,7 +927,11 @@
  */
 static int dump_write(struct file *file, const void *addr, int nr)
 {
-	return file->f_op->write(file, addr, nr, &file->f_pos) == nr;
+	int r;
+	down(&file->f_dentry->d_inode->i_sem);
+	r = file->f_op->write(file, addr, nr, &file->f_pos) == nr;
+	up(&file->f_dentry->d_inode->i_sem);
+	return r;
 }
 
 static int dump_seek(struct file *file, off_t off)
--- linux/arch/sparc64/kernel/binfmt_aout32.c.or	Mon May 10 15:31:47 1999
+++ linux/arch/sparc64/kernel/binfmt_aout32.c	Mon May 10 15:28:33 1999
@@ -57,8 +57,19 @@
  * These are the only things you should do on a core-file: use only these
  * macros to write out all the necessary info.
  */
-#define DUMP_WRITE(addr,nr) \
-while (file->f_op->write(file,(char *)(addr),(nr),&file->f_pos) != (nr)) goto close_coredump
+
+static int dump_write(struct file *file, const void *addr, int nr)
+{
+	int r;
+	down(&file->f_dentry->d_inode->i_sem);
+	r = file->f_op->write(file, addr, nr, &file->f_pos) == nr;
+	up(&file->f_dentry->d_inode->i_sem);
+	return r;
+}
+
+#define DUMP_WRITE(addr, nr)	\
+	if (!dump_write(file, (void *)(addr), (nr))) \
+		goto close_coredump;
 
 #define DUMP_SEEK(offset) \
 if (file->f_op->llseek) { \

-
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