| From bippy-5f407fcff5a0 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-2024-26906: x86/mm: Disallow vsyscall page read for copy_from_kernel_nofault() |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| x86/mm: Disallow vsyscall page read for copy_from_kernel_nofault() |
| |
| When trying to use copy_from_kernel_nofault() to read vsyscall page |
| through a bpf program, the following oops was reported: |
| |
| BUG: unable to handle page fault for address: ffffffffff600000 |
| #PF: supervisor read access in kernel mode |
| #PF: error_code(0x0000) - not-present page |
| PGD 3231067 P4D 3231067 PUD 3233067 PMD 3235067 PTE 0 |
| Oops: 0000 [#1] PREEMPT SMP PTI |
| CPU: 1 PID: 20390 Comm: test_progs ...... 6.7.0+ #58 |
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) ...... |
| RIP: 0010:copy_from_kernel_nofault+0x6f/0x110 |
| ...... |
| Call Trace: |
| <TASK> |
| ? copy_from_kernel_nofault+0x6f/0x110 |
| bpf_probe_read_kernel+0x1d/0x50 |
| bpf_prog_2061065e56845f08_do_probe_read+0x51/0x8d |
| trace_call_bpf+0xc5/0x1c0 |
| perf_call_bpf_enter.isra.0+0x69/0xb0 |
| perf_syscall_enter+0x13e/0x200 |
| syscall_trace_enter+0x188/0x1c0 |
| do_syscall_64+0xb5/0xe0 |
| entry_SYSCALL_64_after_hwframe+0x6e/0x76 |
| </TASK> |
| ...... |
| ---[ end trace 0000000000000000 ]--- |
| |
| The oops is triggered when: |
| |
| 1) A bpf program uses bpf_probe_read_kernel() to read from the vsyscall |
| page and invokes copy_from_kernel_nofault() which in turn calls |
| __get_user_asm(). |
| |
| 2) Because the vsyscall page address is not readable from kernel space, |
| a page fault exception is triggered accordingly. |
| |
| 3) handle_page_fault() considers the vsyscall page address as a user |
| space address instead of a kernel space address. This results in the |
| fix-up setup by bpf not being applied and a page_fault_oops() is invoked |
| due to SMAP. |
| |
| Considering handle_page_fault() has already considered the vsyscall page |
| address as a userspace address, fix the problem by disallowing vsyscall |
| page read for copy_from_kernel_nofault(). |
| |
| The Linux kernel CVE team has assigned CVE-2024-26906 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Fixed in 5.10.214 with commit 6e4694e65b6db4c3de125115dd4f55848cc48381 |
| Fixed in 5.15.153 with commit e8a67fe34b76a49320b33032228a794f40b0316b |
| Fixed in 6.1.83 with commit f175de546a3eb77614d94d4c02550181c0a8493e |
| Fixed in 6.6.23 with commit 57f78c46f08198e1be08ffe99c4c1ccc12855bf5 |
| Fixed in 6.7.11 with commit 29bd6f86904682adafe9affbc7f79b14defcaff8 |
| Fixed in 6.8 with commit 32019c659ecfe1d92e3bf9fcdfbb11a7c70acd58 |
| |
| 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-2024-26906 |
| 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: |
| arch/x86/mm/maccess.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/6e4694e65b6db4c3de125115dd4f55848cc48381 |
| https://git.kernel.org/stable/c/e8a67fe34b76a49320b33032228a794f40b0316b |
| https://git.kernel.org/stable/c/f175de546a3eb77614d94d4c02550181c0a8493e |
| https://git.kernel.org/stable/c/57f78c46f08198e1be08ffe99c4c1ccc12855bf5 |
| https://git.kernel.org/stable/c/29bd6f86904682adafe9affbc7f79b14defcaff8 |
| https://git.kernel.org/stable/c/32019c659ecfe1d92e3bf9fcdfbb11a7c70acd58 |
