| 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-2021-47656: jffs2: fix use-after-free in jffs2_clear_xattr_subsystem |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| jffs2: fix use-after-free in jffs2_clear_xattr_subsystem |
| |
| When we mount a jffs2 image, assume that the first few blocks of |
| the image are normal and contain at least one xattr-related inode, |
| but the next block is abnormal. As a result, an error is returned |
| in jffs2_scan_eraseblock(). jffs2_clear_xattr_subsystem() is then |
| called in jffs2_build_filesystem() and then again in |
| jffs2_do_fill_super(). |
| |
| Finally we can observe the following report: |
| ================================================================== |
| BUG: KASAN: use-after-free in jffs2_clear_xattr_subsystem+0x95/0x6ac |
| Read of size 8 at addr ffff8881243384e0 by task mount/719 |
| |
| Call Trace: |
| dump_stack+0x115/0x16b |
| jffs2_clear_xattr_subsystem+0x95/0x6ac |
| jffs2_do_fill_super+0x84f/0xc30 |
| jffs2_fill_super+0x2ea/0x4c0 |
| mtd_get_sb+0x254/0x400 |
| mtd_get_sb_by_nr+0x4f/0xd0 |
| get_tree_mtd+0x498/0x840 |
| jffs2_get_tree+0x25/0x30 |
| vfs_get_tree+0x8d/0x2e0 |
| path_mount+0x50f/0x1e50 |
| do_mount+0x107/0x130 |
| __se_sys_mount+0x1c5/0x2f0 |
| __x64_sys_mount+0xc7/0x160 |
| do_syscall_64+0x45/0x70 |
| entry_SYSCALL_64_after_hwframe+0x44/0xa9 |
| |
| Allocated by task 719: |
| kasan_save_stack+0x23/0x60 |
| __kasan_kmalloc.constprop.0+0x10b/0x120 |
| kasan_slab_alloc+0x12/0x20 |
| kmem_cache_alloc+0x1c0/0x870 |
| jffs2_alloc_xattr_ref+0x2f/0xa0 |
| jffs2_scan_medium.cold+0x3713/0x4794 |
| jffs2_do_mount_fs.cold+0xa7/0x2253 |
| jffs2_do_fill_super+0x383/0xc30 |
| jffs2_fill_super+0x2ea/0x4c0 |
| [...] |
| |
| Freed by task 719: |
| kmem_cache_free+0xcc/0x7b0 |
| jffs2_free_xattr_ref+0x78/0x98 |
| jffs2_clear_xattr_subsystem+0xa1/0x6ac |
| jffs2_do_mount_fs.cold+0x5e6/0x2253 |
| jffs2_do_fill_super+0x383/0xc30 |
| jffs2_fill_super+0x2ea/0x4c0 |
| [...] |
| |
| The buggy address belongs to the object at ffff8881243384b8 |
| which belongs to the cache jffs2_xattr_ref of size 48 |
| The buggy address is located 40 bytes inside of |
| 48-byte region [ffff8881243384b8, ffff8881243384e8) |
| [...] |
| ================================================================== |
| |
| The triggering of the BUG is shown in the following stack: |
| ----------------------------------------------------------- |
| jffs2_fill_super |
| jffs2_do_fill_super |
| jffs2_do_mount_fs |
| jffs2_build_filesystem |
| jffs2_scan_medium |
| jffs2_scan_eraseblock <--- ERROR |
| jffs2_clear_xattr_subsystem <--- free |
| jffs2_clear_xattr_subsystem <--- free again |
| ----------------------------------------------------------- |
| |
| An error is returned in jffs2_do_mount_fs(). If the error is returned |
| by jffs2_sum_init(), the jffs2_clear_xattr_subsystem() does not need to |
| be executed. If the error is returned by jffs2_build_filesystem(), the |
| jffs2_clear_xattr_subsystem() also does not need to be executed again. |
| So move jffs2_clear_xattr_subsystem() from 'out_inohash' to 'out_root' |
| to fix this UAF problem. |
| |
| The Linux kernel CVE team has assigned CVE-2021-47656 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 2.6.18 with commit aa98d7cf59b5b0764d3502662053489585faf2fe and fixed in 4.9.311 with commit 9150cb625b46f68d524f4cfd491f1aafc23e10a9 |
| Issue introduced in 2.6.18 with commit aa98d7cf59b5b0764d3502662053489585faf2fe and fixed in 4.14.276 with commit 3bd2454162ec6bbb5503233c804fce6e4b6dcec5 |
| Issue introduced in 2.6.18 with commit aa98d7cf59b5b0764d3502662053489585faf2fe and fixed in 4.19.238 with commit c3b07c875fa8f906f932976460fd14798596f101 |
| Issue introduced in 2.6.18 with commit aa98d7cf59b5b0764d3502662053489585faf2fe and fixed in 5.4.189 with commit 30bf7244acf32f19cb722c39f7bc1c2a9f300422 |
| Issue introduced in 2.6.18 with commit aa98d7cf59b5b0764d3502662053489585faf2fe and fixed in 5.10.110 with commit 7bb7428dd73991bf4b3a7a61b493ca50046c2b13 |
| Issue introduced in 2.6.18 with commit aa98d7cf59b5b0764d3502662053489585faf2fe and fixed in 5.15.33 with commit 7a75740206af5f17e9f3efa384211cba70213da1 |
| Issue introduced in 2.6.18 with commit aa98d7cf59b5b0764d3502662053489585faf2fe and fixed in 5.16.19 with commit 22327bd7988f21de3a53c1373f3b81542bfe1f44 |
| Issue introduced in 2.6.18 with commit aa98d7cf59b5b0764d3502662053489585faf2fe and fixed in 5.17.2 with commit 8c0f024f29e055840a5a89fe23b96ae3f921afed |
| Issue introduced in 2.6.18 with commit aa98d7cf59b5b0764d3502662053489585faf2fe and fixed in 5.18 with commit 4c7c44ee1650677fbe89d86edbad9497b7679b5c |
| |
| 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-2021-47656 |
| 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: |
| fs/jffs2/fs.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/9150cb625b46f68d524f4cfd491f1aafc23e10a9 |
| https://git.kernel.org/stable/c/3bd2454162ec6bbb5503233c804fce6e4b6dcec5 |
| https://git.kernel.org/stable/c/c3b07c875fa8f906f932976460fd14798596f101 |
| https://git.kernel.org/stable/c/30bf7244acf32f19cb722c39f7bc1c2a9f300422 |
| https://git.kernel.org/stable/c/7bb7428dd73991bf4b3a7a61b493ca50046c2b13 |
| https://git.kernel.org/stable/c/7a75740206af5f17e9f3efa384211cba70213da1 |
| https://git.kernel.org/stable/c/22327bd7988f21de3a53c1373f3b81542bfe1f44 |
| https://git.kernel.org/stable/c/8c0f024f29e055840a5a89fe23b96ae3f921afed |
| https://git.kernel.org/stable/c/4c7c44ee1650677fbe89d86edbad9497b7679b5c |
