Hi George, kernel test robot noticed the following build warnings: https://git-scm.com/docs/git-format-patch#_base_tree_information] url: https://github.com/intel-lab-lkp/linux/commits/George-Kennedy/vc_screen-reload-load-of-struct-vc_data-pointer-in-vcs_write-to-avoid-UAF/20230510-031202 base: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git tty-testing patch link: https://lore.kernel.org/r/1683659319-29701-1-git-send-email-george.kennedy%40oracle.com patch subject: [PATCH] vc_screen: reload load of struct vc_data pointer in vcs_write() to avoid UAF config: ia64-randconfig-m031-20230509 (https://download.01.org/0day-ci/archive/20230510/202305101936.1ROFaVa9-lkp@xxxxxxxxx/config) compiler: ia64-linux-gcc (GCC) 12.1.0 If you fix the issue, kindly add following tag where applicable | Reported-by: kernel test robot <lkp@xxxxxxxxx> | Reported-by: Dan Carpenter <error27@xxxxxxxxx> | Link: https://lore.kernel.org/r/202305101936.1ROFaVa9-lkp@xxxxxxxxx/ smatch warnings: drivers/tty/vt/vc_screen.c:707 vcs_write() warn: maybe return -EFAULT instead of the bytes remaining? vim +707 drivers/tty/vt/vc_screen.c ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 589 static ssize_t ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 590 vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 591 { 496ad9aa8ef448 drivers/tty/vt/vc_screen.c Al Viro 2013-01-23 592 struct inode *inode = file_inode(file); ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 593 struct vc_data *vc; 95e0d57fd49780 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 594 char *con_buf; 95e0d57fd49780 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 595 u16 *org0, *org; 95e0d57fd49780 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 596 unsigned int written; 2665bef49f96df drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 597 int size; 2665bef49f96df drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 598 ssize_t ret; 2665bef49f96df drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 599 loff_t pos; 2665bef49f96df drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 600 bool viewed, attr; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 601 0c9acb1af77a3c drivers/tty/vt/vc_screen.c Nicolas Pitre 2019-11-05 602 if (use_unicode(inode)) 0c9acb1af77a3c drivers/tty/vt/vc_screen.c Nicolas Pitre 2019-11-05 603 return -EOPNOTSUPP; 0c9acb1af77a3c drivers/tty/vt/vc_screen.c Nicolas Pitre 2019-11-05 604 fcdba07ee390d9 drivers/tty/vt/vc_screen.c Jiri Olsa 2011-02-07 605 con_buf = (char *) __get_free_page(GFP_KERNEL); fcdba07ee390d9 drivers/tty/vt/vc_screen.c Jiri Olsa 2011-02-07 606 if (!con_buf) fcdba07ee390d9 drivers/tty/vt/vc_screen.c Jiri Olsa 2011-02-07 607 return -ENOMEM; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 608 ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 609 pos = *ppos; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 610 ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 611 /* Select the proper current console and verify ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 612 * sanity of the situation under the console lock. ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 613 */ ac751efa6a0d70 drivers/tty/vt/vc_screen.c Torben Hohn 2011-01-25 614 console_lock(); ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 615 d21b0be246bf3b drivers/tty/vt/vc_screen.c Nicolas Pitre 2018-06-26 616 attr = use_attributes(inode); ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 617 ret = -ENXIO; fcdba07ee390d9 drivers/tty/vt/vc_screen.c Jiri Olsa 2011-02-07 618 vc = vcs_vc(inode, &viewed); fcdba07ee390d9 drivers/tty/vt/vc_screen.c Jiri Olsa 2011-02-07 619 if (!vc) ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 620 goto unlock_out; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 621 71d4abfab322e8 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 622 size = vcs_size(vc, attr, false); 71d4abfab322e8 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 623 if (size < 0) { 71d4abfab322e8 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 624 ret = size; 71d4abfab322e8 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 625 goto unlock_out; 71d4abfab322e8 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 626 } ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 627 ret = -EINVAL; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 628 if (pos < 0 || pos > size) ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 629 goto unlock_out; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 630 if (count > size - pos) ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 631 count = size - pos; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 632 written = 0; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 633 while (count) { 95e0d57fd49780 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 634 unsigned int this_round = count; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 635 ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 636 if (this_round > CON_BUF_SIZE) ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 637 this_round = CON_BUF_SIZE; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 638 ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 639 /* Temporarily drop the console lock so that we can read ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 640 * in the write data from userspace safely. ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 641 */ ac751efa6a0d70 drivers/tty/vt/vc_screen.c Torben Hohn 2011-01-25 642 console_unlock(); ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 643 ret = copy_from_user(con_buf, buf, this_round); ac751efa6a0d70 drivers/tty/vt/vc_screen.c Torben Hohn 2011-01-25 644 console_lock(); ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 645 ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 646 if (ret) { ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 647 this_round -= ret; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 648 if (!this_round) { ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 649 /* Abort loop if no data were copied. Otherwise ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 650 * fail with -EFAULT. ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 651 */ ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 652 if (written) ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 653 break; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 654 ret = -EFAULT; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 655 goto unlock_out; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 656 } ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 657 } ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 658 50f4095ab8ede7 drivers/tty/vt/vc_screen.c George Kennedy 2023-05-09 659 /* The vc might have been freed or vcs_size might have changed 50f4095ab8ede7 drivers/tty/vt/vc_screen.c George Kennedy 2023-05-09 660 * while we slept to grab the user buffer, so recheck. ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 661 * Return data written up to now on failure. ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 662 */ 50f4095ab8ede7 drivers/tty/vt/vc_screen.c George Kennedy 2023-05-09 663 vc = vcs_vc(inode, &viewed); 50f4095ab8ede7 drivers/tty/vt/vc_screen.c George Kennedy 2023-05-09 664 if (!vc) { 50f4095ab8ede7 drivers/tty/vt/vc_screen.c George Kennedy 2023-05-09 665 if (written) 50f4095ab8ede7 drivers/tty/vt/vc_screen.c George Kennedy 2023-05-09 666 break; 50f4095ab8ede7 drivers/tty/vt/vc_screen.c George Kennedy 2023-05-09 667 goto unlock_out; The warning message is wrong, but there does need to be a "ret = something" here. Either an error code or ret = size on success. 50f4095ab8ede7 drivers/tty/vt/vc_screen.c George Kennedy 2023-05-09 668 } 71d4abfab322e8 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 669 size = vcs_size(vc, attr, false); dc1892c4bc6960 drivers/tty/vt/vc_screen.c Jiri Olsa 2011-02-07 670 if (size < 0) { dc1892c4bc6960 drivers/tty/vt/vc_screen.c Jiri Olsa 2011-02-07 671 if (written) dc1892c4bc6960 drivers/tty/vt/vc_screen.c Jiri Olsa 2011-02-07 672 break; dc1892c4bc6960 drivers/tty/vt/vc_screen.c Jiri Olsa 2011-02-07 673 ret = size; dc1892c4bc6960 drivers/tty/vt/vc_screen.c Jiri Olsa 2011-02-07 674 goto unlock_out; dc1892c4bc6960 drivers/tty/vt/vc_screen.c Jiri Olsa 2011-02-07 675 } ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 676 if (pos >= size) ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 677 break; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 678 if (this_round > size - pos) ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 679 this_round = size - pos; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 680 ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 681 /* OK, now actually push the write to the console ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 682 * under the lock using the local kernel buffer. ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 683 */ ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 684 95e0d57fd49780 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 685 if (attr) 95e0d57fd49780 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 686 org = vcs_write_buf(vc, con_buf, pos, this_round, 95e0d57fd49780 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 687 viewed, &org0); 95e0d57fd49780 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 688 else 9e6363784e3f1e drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 689 org = vcs_write_buf_noattr(vc, con_buf, pos, this_round, 9e6363784e3f1e drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 690 viewed, &org0); ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 691 95e0d57fd49780 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 692 count -= this_round; 95e0d57fd49780 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 693 written += this_round; 95e0d57fd49780 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 694 buf += this_round; 95e0d57fd49780 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 695 pos += this_round; 95e0d57fd49780 drivers/tty/vt/vc_screen.c Jiri Slaby 2020-08-18 696 if (org) ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 697 update_region(vc, (unsigned long)(org0), org - org0); ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 698 } ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 699 *ppos += written; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 700 ret = written; 432c9ed22aff64 drivers/char/vc_screen.c Nicolas Pitre 2010-10-01 701 if (written) 432c9ed22aff64 drivers/char/vc_screen.c Nicolas Pitre 2010-10-01 702 vcs_scr_updated(vc); ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 703 ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 704 unlock_out: ac751efa6a0d70 drivers/tty/vt/vc_screen.c Torben Hohn 2011-01-25 705 console_unlock(); fcdba07ee390d9 drivers/tty/vt/vc_screen.c Jiri Olsa 2011-02-07 706 free_page((unsigned long) con_buf); ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 @707 return ret; ^1da177e4c3f41 drivers/char/vc_screen.c Linus Torvalds 2005-04-16 708 } -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests
