CVE-2025-38215

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> fbdev: Fix do_register_framebuffer to prevent null-ptr-deref in fb_videomode_to_var<br /> <br /> If fb_add_videomode() in do_register_framebuffer() fails to allocate<br /> memory for fb_videomode, it will later lead to a null-ptr dereference in<br /> fb_videomode_to_var(), as the fb_info is registered while not having the<br /> mode in modelist that is expected to be there, i.e. the one that is<br /> described in fb_info-&gt;var.<br /> <br /> ================================================================<br /> general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN NOPTI<br /> KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]<br /> CPU: 1 PID: 30371 Comm: syz-executor.1 Not tainted 5.10.226-syzkaller #0<br /> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014<br /> RIP: 0010:fb_videomode_to_var+0x24/0x610 drivers/video/fbdev/core/modedb.c:901<br /> Call Trace:<br /> display_to_var+0x3a/0x7c0 drivers/video/fbdev/core/fbcon.c:929<br /> fbcon_resize+0x3e2/0x8f0 drivers/video/fbdev/core/fbcon.c:2071<br /> resize_screen drivers/tty/vt/vt.c:1176 [inline]<br /> vc_do_resize+0x53a/0x1170 drivers/tty/vt/vt.c:1263<br /> fbcon_modechanged+0x3ac/0x6e0 drivers/video/fbdev/core/fbcon.c:2720<br /> fbcon_update_vcs+0x43/0x60 drivers/video/fbdev/core/fbcon.c:2776<br /> do_fb_ioctl+0x6d2/0x740 drivers/video/fbdev/core/fbmem.c:1128<br /> fb_ioctl+0xe7/0x150 drivers/video/fbdev/core/fbmem.c:1203<br /> vfs_ioctl fs/ioctl.c:48 [inline]<br /> __do_sys_ioctl fs/ioctl.c:753 [inline]<br /> __se_sys_ioctl fs/ioctl.c:739 [inline]<br /> __x64_sys_ioctl+0x19a/0x210 fs/ioctl.c:739<br /> do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46<br /> entry_SYSCALL_64_after_hwframe+0x67/0xd1<br /> ================================================================<br /> <br /> Even though fbcon_init() checks beforehand if fb_match_mode() in<br /> var_to_display() fails, it can not prevent the panic because fbcon_init()<br /> does not return error code. Considering this and the comment in the code<br /> about fb_match_mode() returning NULL - "This should not happen" - it is<br /> better to prevent registering the fb_info if its mode was not set<br /> successfully. Also move fb_add_videomode() closer to the beginning of<br /> do_register_framebuffer() to avoid having to do the cleanup on fail.<br /> <br /> Found by Linux Verification Center (linuxtesting.org) with Syzkaller.