make dump_emit() use vfs_write() instead of banging at ->f_op->write directly

... and deal with short writes properly - the output might be to pipe, after
all; as it is, e.g. no-MMU case of elf_fdpic coredump can write a whole lot
more than a page worth of data at one call.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 12 insertions, 5 deletions

diff --git a/fs/coredump.c b/fs/coredump.c
index 319f973bab72..2472ed9e682c 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -696,13 +696,20 @@ EXPORT_SYMBOL(dump_write);
 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
 {
         struct file *file = cprm->file;
-        if (dump_interrupted() || !access_ok(VERIFY_READ, addr, nr))
-                return 0;
+        loff_t pos = file->f_pos;
+        ssize_t n;
         if (cprm->written + nr > cprm->limit)
                 return 0;
-        if (file->f_op->write(file, addr, nr, &file->f_pos) != nr)
-                return 0;
-        cprm->written += nr;
+        while (nr) {
+                if (dump_interrupted())
+                        return 0;
+                n = vfs_write(file, addr, nr, &pos);
+                if (n <= 0)
+                        return 0;
+                file->f_pos = pos;
+                cprm->written += n;
+                nr -= n;
+        }
         return 1;
 }
 EXPORT_SYMBOL(dump_emit);