| From bippy-7c5fe7eed585 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2025-21976: fbdev: hyperv_fb: Allow graceful removal of framebuffer |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| fbdev: hyperv_fb: Allow graceful removal of framebuffer |
| |
| When a Hyper-V framebuffer device is unbind, hyperv_fb driver tries to |
| release the framebuffer forcefully. If this framebuffer is in use it |
| produce the following WARN and hence this framebuffer is never released. |
| |
| [ 44.111220] WARNING: CPU: 35 PID: 1882 at drivers/video/fbdev/core/fb_info.c:70 framebuffer_release+0x2c/0x40 |
| < snip > |
| [ 44.111289] Call Trace: |
| [ 44.111290] <TASK> |
| [ 44.111291] ? show_regs+0x6c/0x80 |
| [ 44.111295] ? __warn+0x8d/0x150 |
| [ 44.111298] ? framebuffer_release+0x2c/0x40 |
| [ 44.111300] ? report_bug+0x182/0x1b0 |
| [ 44.111303] ? handle_bug+0x6e/0xb0 |
| [ 44.111306] ? exc_invalid_op+0x18/0x80 |
| [ 44.111308] ? asm_exc_invalid_op+0x1b/0x20 |
| [ 44.111311] ? framebuffer_release+0x2c/0x40 |
| [ 44.111313] ? hvfb_remove+0x86/0xa0 [hyperv_fb] |
| [ 44.111315] vmbus_remove+0x24/0x40 [hv_vmbus] |
| [ 44.111323] device_remove+0x40/0x80 |
| [ 44.111325] device_release_driver_internal+0x20b/0x270 |
| [ 44.111327] ? bus_find_device+0xb3/0xf0 |
| |
| Fix this by moving the release of framebuffer and assosiated memory |
| to fb_ops.fb_destroy function, so that framebuffer framework handles |
| it gracefully. |
| |
| While we fix this, also replace manual registrations/unregistration of |
| framebuffer with devm_register_framebuffer. |
| |
| The Linux kernel CVE team has assigned CVE-2025-21976 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 3.10 with commit 68a2d20b79b105f02dcbc52c211d7e62f98996b7 and fixed in 6.12.20 with commit 4545e2aa121aea304d33903099c03e29ed4fe50a |
| Issue introduced in 3.10 with commit 68a2d20b79b105f02dcbc52c211d7e62f98996b7 and fixed in 6.13.8 with commit a7b583dc99c6cf4a96877017be1d08247e1ef2c7 |
| Issue introduced in 3.10 with commit 68a2d20b79b105f02dcbc52c211d7e62f98996b7 and fixed in 6.14 with commit ea2f45ab0e53b255f72c85ccd99e2b394fc5fceb |
| |
| 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-2025-21976 |
| 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/hyperv_fb.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/4545e2aa121aea304d33903099c03e29ed4fe50a |
| https://git.kernel.org/stable/c/a7b583dc99c6cf4a96877017be1d08247e1ef2c7 |
| https://git.kernel.org/stable/c/ea2f45ab0e53b255f72c85ccd99e2b394fc5fceb |
