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pipe(2) - race-free error recovery

don't mess with sys_close() if copy_to_user() fails; just postpone
fd_install() until we know it hasn't.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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1 parent a79f41e commit 5b249b1b07c42c61d0c53b8ab4fad026e39a9be9 Al Viro committed Aug 19, 2012
Showing with 22 additions and 9 deletions.
  1. +22 −9 fs/pipe.c
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@@ -1064,9 +1064,8 @@ int create_pipe_files(struct file **res, int flags)
return err;
}
-int do_pipe_flags(int *fd, int flags)
+static int __do_pipe_flags(int *fd, struct file **files, int flags)
{
- struct file *files[2];
int error;
int fdw, fdr;
@@ -1088,11 +1087,8 @@ int do_pipe_flags(int *fd, int flags)
fdw = error;
audit_fd_pair(fdr, fdw);
- fd_install(fdr, files[0]);
- fd_install(fdw, files[1]);
fd[0] = fdr;
fd[1] = fdw;
-
return 0;
err_fdr:
@@ -1103,21 +1099,38 @@ int do_pipe_flags(int *fd, int flags)
return error;
}
+int do_pipe_flags(int *fd, int flags)
+{
+ struct file *files[2];
+ int error = __do_pipe_flags(fd, files, flags);
+ if (!error) {
+ fd_install(fd[0], files[0]);
+ fd_install(fd[1], files[1]);
+ }
+ return error;
+}
+
/*
* sys_pipe() is the normal C calling standard for creating
* a pipe. It's not the way Unix traditionally does this, though.
*/
SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
{
+ struct file *files[2];
int fd[2];
int error;
- error = do_pipe_flags(fd, flags);
+ error = __do_pipe_flags(fd, files, flags);
if (!error) {
- if (copy_to_user(fildes, fd, sizeof(fd))) {
- sys_close(fd[0]);
- sys_close(fd[1]);
+ if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
+ fput(files[0]);
+ fput(files[1]);
+ put_unused_fd(fd[0]);
+ put_unused_fd(fd[1]);
error = -EFAULT;
+ } else {
+ fd_install(fd[0], files[0]);
+ fd_install(fd[1], files[1]);
}
}
return error;

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