ghsa-wm99-2g28-jp5m
Vulnerability from github
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:
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": [],
"aliases": [
"CVE-2024-26798"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-04-04T09:15:08Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nfbcon: always restore the old font data in fbcon_do_set_font()\n\nCommit a5a923038d70 (fbdev: fbcon: Properly revert changes when\nvc_resize() failed) started restoring old font data upon failure (of\nvc_resize()). But it performs so only for user fonts. It means that the\n\"system\"/internal fonts are not restored at all. So in result, the very\nfirst call to fbcon_do_set_font() performs no restore at all upon\nfailing vc_resize().\n\nThis can be reproduced by Syzkaller to crash the system on the next\ninvocation of font_get(). It\u0027s rather hard to hit the allocation failure\nin vc_resize() on the first font_set(), but not impossible. Esp. if\nfault injection is used to aid the execution/failure. It was\ndemonstrated by Sirius:\n BUG: unable to handle page fault for address: fffffffffffffff8\n #PF: supervisor read access in kernel mode\n #PF: error_code(0x0000) - not-present page\n PGD cb7b067 P4D cb7b067 PUD cb7d067 PMD 0\n Oops: 0000 [#1] PREEMPT SMP KASAN\n CPU: 1 PID: 8007 Comm: poc Not tainted 6.7.0-g9d1694dc91ce #20\n Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014\n RIP: 0010:fbcon_get_font+0x229/0x800 drivers/video/fbdev/core/fbcon.c:2286\n Call Trace:\n \u003cTASK\u003e\n con_font_get drivers/tty/vt/vt.c:4558 [inline]\n con_font_op+0x1fc/0xf20 drivers/tty/vt/vt.c:4673\n vt_k_ioctl drivers/tty/vt/vt_ioctl.c:474 [inline]\n vt_ioctl+0x632/0x2ec0 drivers/tty/vt/vt_ioctl.c:752\n tty_ioctl+0x6f8/0x1570 drivers/tty/tty_io.c:2803\n vfs_ioctl fs/ioctl.c:51 [inline]\n ...\n\nSo restore the font data in any case, not only for user fonts. Note the\nlater \u0027if\u0027 is now protected by \u0027old_userfont\u0027 and not \u0027old_data\u0027 as the\nlatter is always set now. (And it is supposed to be non-NULL. Otherwise\nwe would see the bug above again.)",
"id": "GHSA-wm99-2g28-jp5m",
"modified": "2024-04-04T09:30:36Z",
"published": "2024-04-04T09:30:36Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-26798"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/00d6a284fcf3fad1b7e1b5bc3cd87cbfb60ce03f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/20a4b5214f7bee13c897477168c77bbf79683c3d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2f91a96b892fab2f2543b4a55740c5bee36b1a6b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/73a6bd68a1342f3a44cac9dffad81ad6a003e520"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a2c881413dcc5d801bdc9535e51270cc88cb9cd8"
}
],
"schema_version": "1.4.0",
"severity": []
}