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CVE PROGRAM SOURCE RECORDUnscored

CVE-2024-26798

fbcon: always restore the old font data in fbcon_do_set_font()

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Status
Published
Published
Updated
Assigning organization
Linux

Description

In the Linux kernel, the following vulnerability has been resolved: fbcon: always restore the old font data in fbcon_do_set_font() Commit a5a923038d70 (fbdev: fbcon: Properly revert changes when vc_resize() failed) started restoring old font data upon failure (of vc_resize()). But it performs so only for user fonts. It means that the "system"/internal fonts are not restored at all. So in result, the very first call to fbcon_do_set_font() performs no restore at all upon failing vc_resize(). This can be reproduced by Syzkaller to crash the system on the next invocation of font_get(). It's rather hard to hit the allocation failure in vc_resize() on the first font_set(), but not impossible. Esp. if fault injection is used to aid the execution/failure. It was demonstrated by Sirius: BUG: unable to handle page fault for address: fffffffffffffff8 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD cb7b067 P4D cb7b067 PUD cb7d067 PMD 0 Oops: 0000 [#1] PREEMPT SMP KASAN CPU: 1 PID: 8007 Comm: poc Not tainted 6.7.0-g9d1694dc91ce #20 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 RIP: 0010:fbcon_get_font+0x229/0x800 drivers/video/fbdev/core/fbcon.c:2286 Call Trace: <TASK> con_font_get drivers/tty/vt/vt.c:4558 [inline] con_font_op+0x1fc/0xf20 drivers/tty/vt/vt.c:4673 vt_k_ioctl drivers/tty/vt/vt_ioctl.c:474 [inline] vt_ioctl+0x632/0x2ec0 drivers/tty/vt/vt_ioctl.c:752 tty_ioctl+0x6f8/0x1570 drivers/tty/tty_io.c:2803 vfs_ioctl fs/ioctl.c:51 [inline] ... So restore the font data in any case, not only for user fonts. Note the later 'if' is now protected by 'old_userfont' and not 'old_data' as the latter is always set now. (And it is supposed to be non-NULL. Otherwise we would see the bug above again.)

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 868749a7456dc48e93887a8474194e2ee6d6c21f to < ae68f57df3335679653868fafccd8c88ef84ae98affected
  • ebd6f886aa2447fcfcdce5450c9e1028e1d681bb to < 20a4b5214f7bee13c897477168c77bbf79683c3daffected
  • a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 to < 2f91a96b892fab2f2543b4a55740c5bee36b1a6baffected
  • a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 to < 73a6bd68a1342f3a44cac9dffad81ad6a003e520affected
  • a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 to < a2c881413dcc5d801bdc9535e51270cc88cb9cd8affected
  • a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 to < 00d6a284fcf3fad1b7e1b5bc3cd87cbfb60ce03faffected
  • f08ccb792d3eaf1dc62d8cbf6a30d6522329f660affected
  • 5.15.64 to < 5.15.151affected
  • 5.19.6 to < 5.20affected

Linux Linux

Default version status: affected

  • 6.0affected
  • 0 to < 6.0unaffected
  • 5.15.151 to ≤ 5.15.*unaffected
  • 6.1.81 to ≤ 6.1.*unaffected
  • 6.6.21 to ≤ 6.6.*unaffected
  • 6.7.9 to ≤ 6.7.*unaffected
  • 6.8 to ≤ *unaffected

References