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Message-ID: <2025070423-CVE-2025-38214-539a@gregkh> Date: Fri, 4 Jul 2025 15:37:43 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-cve-announce@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...nel.org> Subject: CVE-2025-38214: fbdev: Fix fb_set_var to prevent null-ptr-deref in fb_videomode_to_var From: Greg Kroah-Hartman <gregkh@...nel.org> Description =========== In the Linux kernel, the following vulnerability has been resolved: fbdev: Fix fb_set_var to prevent null-ptr-deref in fb_videomode_to_var If fb_add_videomode() in fb_set_var() fails to allocate memory for fb_videomode, later it may lead to a null-ptr dereference in fb_videomode_to_var(), as the fb_info is registered while not having the mode in modelist that is expected to be there, i.e. the one that is described in fb_info->var. ================================================================ general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] CPU: 1 PID: 30371 Comm: syz-executor.1 Not tainted 5.10.226-syzkaller #0 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 RIP: 0010:fb_videomode_to_var+0x24/0x610 drivers/video/fbdev/core/modedb.c:901 Call Trace: display_to_var+0x3a/0x7c0 drivers/video/fbdev/core/fbcon.c:929 fbcon_resize+0x3e2/0x8f0 drivers/video/fbdev/core/fbcon.c:2071 resize_screen drivers/tty/vt/vt.c:1176 [inline] vc_do_resize+0x53a/0x1170 drivers/tty/vt/vt.c:1263 fbcon_modechanged+0x3ac/0x6e0 drivers/video/fbdev/core/fbcon.c:2720 fbcon_update_vcs+0x43/0x60 drivers/video/fbdev/core/fbcon.c:2776 do_fb_ioctl+0x6d2/0x740 drivers/video/fbdev/core/fbmem.c:1128 fb_ioctl+0xe7/0x150 drivers/video/fbdev/core/fbmem.c:1203 vfs_ioctl fs/ioctl.c:48 [inline] __do_sys_ioctl fs/ioctl.c:753 [inline] __se_sys_ioctl fs/ioctl.c:739 [inline] __x64_sys_ioctl+0x19a/0x210 fs/ioctl.c:739 do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x67/0xd1 ================================================================ The reason is that fb_info->var is being modified in fb_set_var(), and then fb_videomode_to_var() is called. If it fails to add the mode to fb_info->modelist, fb_set_var() returns error, but does not restore the old value of fb_info->var. Restore fb_info->var on failure the same way it is done earlier in the function. Found by Linux Verification Center (linuxtesting.org) with Syzkaller. The Linux kernel CVE team has assigned CVE-2025-38214 to this issue. Affected and fixed versions =========================== Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 5.4.295 with commit ee20216f12d9482cd70e44dae5e7fabb38367c71 Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 5.10.239 with commit fab201d72fde38d081e2c5d4ad25595c535b7b22 Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 5.15.186 with commit 1a10d91766eb6ddfd5414e4785611e33a4fe0f9b Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.1.142 with commit ff0e037241173b574b385bff53d67567b9816db5 Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.6.95 with commit 3ca78032a388a0795201792b36e6fc9b6e6e8eed Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.12.35 with commit b3071bb463ea1e6c686d0dc9638fc940f2f5cf17 Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.15.4 with commit 8a3a2887794b2c8e78b3e5d6e3de724527c9f41b Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.16-rc1 with commit 05f6e183879d9785a3cdf2f08a498bc31b7a20aa Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2025-38214 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: drivers/video/fbdev/core/fbmem.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/ee20216f12d9482cd70e44dae5e7fabb38367c71 https://git.kernel.org/stable/c/fab201d72fde38d081e2c5d4ad25595c535b7b22 https://git.kernel.org/stable/c/1a10d91766eb6ddfd5414e4785611e33a4fe0f9b https://git.kernel.org/stable/c/ff0e037241173b574b385bff53d67567b9816db5 https://git.kernel.org/stable/c/3ca78032a388a0795201792b36e6fc9b6e6e8eed https://git.kernel.org/stable/c/b3071bb463ea1e6c686d0dc9638fc940f2f5cf17 https://git.kernel.org/stable/c/8a3a2887794b2c8e78b3e5d6e3de724527c9f41b https://git.kernel.org/stable/c/05f6e183879d9785a3cdf2f08a498bc31b7a20aa
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