| 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-2024-42293: arm64: mm: Fix lockless walks with static and dynamic page-table folding |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| arm64: mm: Fix lockless walks with static and dynamic page-table folding |
| |
| Lina reports random oopsen originating from the fast GUP code when |
| 16K pages are used with 4-level page-tables, the fourth level being |
| folded at runtime due to lack of LPA2. |
| |
| In this configuration, the generic implementation of |
| p4d_offset_lockless() will return a 'p4d_t *' corresponding to the |
| 'pgd_t' allocated on the stack of the caller, gup_fast_pgd_range(). |
| This is normally fine, but when the fourth level of page-table is folded |
| at runtime, pud_offset_lockless() will offset from the address of the |
| 'p4d_t' to calculate the address of the PUD in the same page-table page. |
| This results in a stray stack read when the 'p4d_t' has been allocated |
| on the stack and can send the walker into the weeds. |
| |
| Fix the problem by providing our own definition of p4d_offset_lockless() |
| when CONFIG_PGTABLE_LEVELS <= 4 which returns the real page-table |
| pointer rather than the address of the local stack variable. |
| |
| The Linux kernel CVE team has assigned CVE-2024-42293 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.9 with commit 0dd4f60a2c76938c2625f6c630c225699d97608b and fixed in 6.10.3 with commit 78672d49d3eebbcda3589f4d6e589caf357c5a59 |
| Issue introduced in 6.9 with commit 0dd4f60a2c76938c2625f6c630c225699d97608b and fixed in 6.11 with commit 36639013b3462c06ff8e3400a427f775b4fc97f5 |
| |
| 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-2024-42293 |
| 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/arm64/include/asm/pgtable.h |
| |
| |
| 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/78672d49d3eebbcda3589f4d6e589caf357c5a59 |
| https://git.kernel.org/stable/c/36639013b3462c06ff8e3400a427f775b4fc97f5 |
