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Subject[PATCH] fbcon: fix null-ptr-deref in fbcon_switch
Date
Add check for vc_cons[logo_shown].d, as it can be released by
vt_ioctl(VT_DISALLOCATE).

Reported-by: syzbot+732528bae351682f1f27@syzkaller.appspotmail.com
Signed-off-by: Qiujun Huang <hqjagain@gmail.com>
---
drivers/video/fbdev/core/fbcon.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index bb6ae995c2e5..7ee0f7b55829 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -2254,7 +2254,7 @@ static int fbcon_switch(struct vc_data *vc)
fbcon_update_softback(vc);
}

- if (logo_shown >= 0) {
+ if (logo_shown >= 0 && vc_cons_allocated(logo_shown)) {
struct vc_data *conp2 = vc_cons[logo_shown].d;

if (conp2->vc_top == logo_lines
@@ -2852,7 +2852,7 @@ static void fbcon_scrolldelta(struct vc_data *vc, int lines)
return;
if (vc->vc_mode != KD_TEXT || !lines)
return;
- if (logo_shown >= 0) {
+ if (logo_shown >= 0 && vc_cons_allocated(logo_shown)) {
struct vc_data *conp2 = vc_cons[logo_shown].d;

if (conp2->vc_top == logo_lines
--
2.17.1
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