kernel/linux.git/drivers/tty/vt, branch v4.19.77

vt/fbcon: deinitialize resources in visual_init() after failed memory allocation

2019-06-09T07:17:21+00:00

commit a1ad1cc9704f64c169261a76e1aee1cf1ae51832 upstream. After memory allocation failure vc_allocate() doesn't clean up data which has been initialized in visual_init(). In case of fbcon this leads to divide-by-0 in fbcon_init() on next open of the same tty. memory allocation in vc_allocate() may fail here: 1097: vc->vc_screenbuf = kzalloc(vc->vc_screenbuf_size, GFP_KERNEL); on next open() fbcon_init() skips vc_font.data initialization: 1088: if (!p->fontdata) { division by zero in fbcon_init() happens here: 1149: new_cols /= vc->vc_font.width; Additional check is needed in fbcon_deinit() to prevent usage of uninitialized vc_screenbuf: 1251: if (vc->vc_hi_font_mask && vc->vc_screenbuf) 1252: set_vc_hi_font(vc, false); Crash: #6 [ffffc90001eafa60] divide_error at ffffffff81a00be4 [exception RIP: fbcon_init+463] RIP: ffffffff814b860f RSP: ffffc90001eafb18 RFLAGS: 00010246 ... #7 [ffffc90001eafb60] visual_init at ffffffff8154c36e #8 [ffffc90001eafb80] vc_allocate at ffffffff8154f53c #9 [ffffc90001eafbc8] con_install at ffffffff8154f624 ... Signed-off-by: Grzegorz Halat Reviewed-by: Oleksandr Natalenko Acked-by: Bartlomiej Zolnierkiewicz Cc: stable Signed-off-by: Greg Kroah-Hartman

tty/vt: fix write/write race in ioctl(KDSKBSENT) handler

2019-05-22T05:37:41+00:00

commit 46ca3f735f345c9d87383dd3a09fa5d43870770e upstream. The bug manifests as an attempt to access deallocated memory: BUG: unable to handle kernel paging request at ffff9c8735448000 #PF error: [PROT] [WRITE] PGD 288a05067 P4D 288a05067 PUD 288a07067 PMD 7f60c2063 PTE 80000007f5448161 Oops: 0003 [#1] PREEMPT SMP CPU: 6 PID: 388 Comm: loadkeys Tainted: G C 5.0.0-rc6-00153-g5ded5871030e #91 Hardware name: Gigabyte Technology Co., Ltd. To be filled by O.E.M./H77M-D3H, BIOS F12 11/14/2013 RIP: 0010:__memmove+0x81/0x1a0 Code: 4c 89 4f 10 4c 89 47 18 48 8d 7f 20 73 d4 48 83 c2 20 e9 a2 00 00 00 66 90 48 89 d1 4c 8b 5c 16 f8 4c 8d 54 17 f8 48 c1 e9 03 48 a5 4d 89 1a e9 0c 01 00 00 0f 1f 40 00 48 89 d1 4c 8b 1e 49 RSP: 0018:ffffa1b9002d7d08 EFLAGS: 00010203 RAX: ffff9c873541af43 RBX: ffff9c873541af43 RCX: 00000c6f105cd6bf RDX: 0000637882e986b6 RSI: ffff9c8735447ffb RDI: ffff9c8735447ffb RBP: ffff9c8739cd3800 R08: ffff9c873b802f00 R09: 00000000fffff73b R10: ffffffffb82b35f1 R11: 00505b1b004d5b1b R12: 0000000000000000 R13: ffff9c873541af3d R14: 000000000000000b R15: 000000000000000c FS: 00007f450c390580(0000) GS:ffff9c873f180000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffff9c8735448000 CR3: 00000007e213c002 CR4: 00000000000606e0 Call Trace: vt_do_kdgkb_ioctl+0x34d/0x440 vt_ioctl+0xba3/0x1190 ? __bpf_prog_run32+0x39/0x60 ? mem_cgroup_commit_charge+0x7b/0x4e0 tty_ioctl+0x23f/0x920 ? preempt_count_sub+0x98/0xe0 ? __seccomp_filter+0x67/0x600 do_vfs_ioctl+0xa2/0x6a0 ? syscall_trace_enter+0x192/0x2d0 ksys_ioctl+0x3a/0x70 __x64_sys_ioctl+0x16/0x20 do_syscall_64+0x54/0xe0 entry_SYSCALL_64_after_hwframe+0x49/0xbe The bug manifests on systemd systems with multiple vtcon devices: # cat /sys/devices/virtual/vtconsole/vtcon0/name (S) dummy device # cat /sys/devices/virtual/vtconsole/vtcon1/name (M) frame buffer device There systemd runs 'loadkeys' tool in tapallel for each vtcon instance. This causes two parallel ioctl(KDSKBSENT) calls to race into adding the same entry into 'func_table' array at: drivers/tty/vt/keyboard.c:vt_do_kdgkb_ioctl() The function has no locking around writes to 'func_table'. The simplest reproducer is to have initrams with the following init on a 8-CPU machine x86_64: #!/bin/sh loadkeys -q windowkeys ru4 & loadkeys -q windowkeys ru4 & loadkeys -q windowkeys ru4 & loadkeys -q windowkeys ru4 & loadkeys -q windowkeys ru4 & loadkeys -q windowkeys ru4 & loadkeys -q windowkeys ru4 & loadkeys -q windowkeys ru4 & wait The change adds lock on write path only. Reads are still racy. CC: Greg Kroah-Hartman CC: Jiri Slaby Link: https://lkml.org/lkml/2019/2/17/256 Signed-off-by: Sergei Trofimovich Cc: stable Signed-off-by: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman

tty: vt.c: Fix TIOCL_BLANKSCREEN console blanking if blankinterval == 0

2019-05-22T05:37:41+00:00

commit 75ddbc1fb11efac87b611d48e9802f6fe2bb2163 upstream. Previously, in the userspace, it was possible to use the "setterm" command from util-linux to blank the VT console by default, using the following command. According to the man page, > The force option keeps the screen blank even if a key is pressed. It was implemented by calling TIOCL_BLANKSCREEN. case BLANKSCREEN: ioctlarg = TIOCL_BLANKSCREEN; if (ioctl(STDIN_FILENO, TIOCLINUX, &ioctlarg)) warn(_("cannot force blank")); break; However, after Linux 4.12, this command ceased to work anymore, which is unexpected. By inspecting the kernel source, it shows that the issue was triggered by the side-effect from commit a4199f5eb809 ("tty: Disable default console blanking interval"). The console blanking is implemented by function do_blank_screen() in vt.c: "blank_state" will be initialized to "blank_normal_wait" in con_init() if AND ONLY IF ("blankinterval" > 0). If "blankinterval" is 0, "blank_state" will be "blank_off" (== 0), and a call to do_blank_screen() will always abort, even if a forced blanking is required from the user by calling TIOCL_BLANKSCREEN, the console won't be blanked. This behavior is unexpected from a user's point-of-view, since it's not mentioned in any documentation. The setterm man page suggests it will always work, and the kernel comments in uapi/linux/tiocl.h says > /* keep screen blank even if a key is pressed */ > #define TIOCL_BLANKSCREEN 14 To fix it, we simply remove the "blank_state != blank_off" check, as pointed out by Nicolas Pitre, this check doesn't logically make sense and it's safe to remove. Suggested-by: Nicolas Pitre Fixes: a4199f5eb809 ("tty: Disable default console blanking interval") Signed-off-by: Yifeng Li Cc: stable Signed-off-by: Greg Kroah-Hartman

vt: fix cursor when clearing the screen

2019-04-27T07:36:36+00:00

commit b2ecf00631362a83744e5ec249947620db5e240c upstream. The patch a6dbe4427559 ("vt: perform safe console erase in the right order") introduced a bug. The conditional do_update_region() was replaced by a call to update_region() that does contain the conditional already, but with unwanted extra side effects such as restoring the cursor drawing. In order to reproduce the bug: - use framebuffer console with the AMDGPU driver - type "links" to start the console www browser - press 'q' and space to exit links Now the cursor will be permanently visible in the center of the screen. It will stay there until something overwrites it. The bug goes away if we change update_region() back to the conditional do_update_region(). [ nico: reworded changelog ] Signed-off-by: Mikulas Patocka Reviewed-by: Nicolas Pitre Cc: stable@vger.kernel.org Fixes: a6dbe4427559 ("vt: perform safe console erase in the right order") Signed-off-by: Greg Kroah-Hartman

vt: perform safe console erase in the right order

2019-03-23T19:10:10+00:00

commit a6dbe442755999960ca54a9b8ecfd9606be0ea75 upstream. Commit 4b4ecd9cb853 ("vt: Perform safe console erase only once") removed what appeared to be an extra call to scr_memsetw(). This missed the fact that set_origin() must be called before clearing the screen otherwise old screen content gets restored on the screen when using vgacon. Let's fix that by moving all the scrollback handling to flush_scrollback() where it logically belongs, and invoking it before the actual screen clearing in csi_J(), making the code simpler in the end. Reported-by: Matthew Whitehead Signed-off-by: Nicolas Pitre Tested-by: Matthew Whitehead Fixes: 4b4ecd9cb853 ("vt: Perform safe console erase only once") Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman

vt: invoke notifier on screen size change

2019-01-31T07:14:40+00:00

commit 0c9b1965faddad7534b6974b5b36c4ad37998f8e upstream. User space using poll() on /dev/vcs devices are not awaken when a screen size change occurs. Let's fix that. Signed-off-by: Nicolas Pitre Cc: stable Signed-off-by: Greg Kroah-Hartman

vt: always call notifier with the console lock held

2019-01-31T07:14:40+00:00

commit 7e1d226345f89ad5d0216a9092c81386c89b4983 upstream. Every invocation of notify_write() and notify_update() is performed under the console lock, except for one case. Let's fix that. Signed-off-by: Nicolas Pitre Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman

vt: make vt_console_print() compatible with the unicode screen buffer

2019-01-31T07:14:39+00:00

commit 6609cff65c5b184ab889880ef5d41189611ea05f upstream. When kernel messages are printed to the console, they appear blank on the unicode screen. This is because vt_console_print() is lacking a call to vc_uniscr_putc(). However the later function assumes vc->vc_x is always up to date when called, which is not the case here as vt_console_print() uses it to mark the beginning of the display update. This patch reworks (and simplifies) vt_console_print() so that vc->vc_x is always valid and keeps the start of display update in a local variable instead, which finally allows for adding the missing vc_uniscr_putc() call. Signed-off-by: Nicolas Pitre Cc: stable@vger.kernel.org # v4.19+ Signed-off-by: Greg Kroah-Hartman

vt: fix broken display when running aptitude

2018-11-13T19:09:00+00:00

commit 943210ba807ec50aafa2fa7b13bd6d36a478969b upstream. If you run aptitude on framebuffer console, the display is corrupted. The corruption is caused by the commit d8ae7242. The patch adds "offset" to "start" when calling scr_memsetw, but it forgets to do the same addition on a subsequent call to do_update_region. Signed-off-by: Mikulas Patocka Fixes: d8ae72427187 ("vt: preserve unicode values corresponding to screen characters") Reviewed-by: Nicolas Pitre Cc: stable@vger.kernel.org # 4.19 Signed-off-by: Greg Kroah-Hartman

tty: vt_ioctl: fix potential Spectre v1

2018-09-18T13:51:30+00:00

vsa.console is indirectly controlled by user-space, hence leading to a potential exploitation of the Spectre variant 1 vulnerability. This issue was detected with the help of Smatch: drivers/tty/vt/vt_ioctl.c:711 vt_ioctl() warn: potential spectre issue 'vc_cons' [r] Fix this by sanitizing vsa.console before using it to index vc_cons Notice that given that speculation windows are large, the policy is to kill the speculation on the first load and not worry if it can be completed with a dependent load/store [1]. [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2 Cc: stable@vger.kernel.org Signed-off-by: Gustavo A. R. Silva Reviewed-by: Alan Cox Signed-off-by: Greg Kroah-Hartman