vfs: missed source of ->f_pos races

compat_sys_{read,write}v() need the same "pass a copy of file->f_pos" thing
as sys_{read,write}{,v}().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 2 deletions

diff --git a/fs/compat.c b/fs/compat.c
index 6161255fac45..1bdb350ea5d3 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1155,11 +1155,14 @@ compat_sys_readv(unsigned long fd, const struct compat_iovec __user *vec,
         struct file *file;
         int fput_needed;
         ssize_t ret;
+        loff_t pos;
 
         file = fget_light(fd, &fput_needed);
         if (!file)
                 return -EBADF;
-        ret = compat_readv(file, vec, vlen, &file->f_pos);
+        pos = file->f_pos;
+        ret = compat_readv(file, vec, vlen, &pos);
+        file->f_pos = pos;
         fput_light(file, fput_needed);
         return ret;
 }
@@ -1221,11 +1224,14 @@ compat_sys_writev(unsigned long fd, const struct compat_iovec __user *vec,
         struct file *file;
         int fput_needed;
         ssize_t ret;
+        loff_t pos;
 
         file = fget_light(fd, &fput_needed);
         if (!file)
                 return -EBADF;
-        ret = compat_writev(file, vec, vlen, &file->f_pos);
+        pos = file->f_pos;
+        ret = compat_writev(file, vec, vlen, &pos);
+        file->f_pos = pos;
         fput_light(file, fput_needed);
         return ret;
 }