| 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-2024-26727: btrfs: do not ASSERT() if the newly created subvolume already got read |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| btrfs: do not ASSERT() if the newly created subvolume already got read |
| |
| [BUG] |
| There is a syzbot crash, triggered by the ASSERT() during subvolume |
| creation: |
| |
| assertion failed: !anon_dev, in fs/btrfs/disk-io.c:1319 |
| ------------[ cut here ]------------ |
| kernel BUG at fs/btrfs/disk-io.c:1319! |
| invalid opcode: 0000 [#1] PREEMPT SMP KASAN |
| RIP: 0010:btrfs_get_root_ref.part.0+0x9aa/0xa60 |
| <TASK> |
| btrfs_get_new_fs_root+0xd3/0xf0 |
| create_subvol+0xd02/0x1650 |
| btrfs_mksubvol+0xe95/0x12b0 |
| __btrfs_ioctl_snap_create+0x2f9/0x4f0 |
| btrfs_ioctl_snap_create+0x16b/0x200 |
| btrfs_ioctl+0x35f0/0x5cf0 |
| __x64_sys_ioctl+0x19d/0x210 |
| do_syscall_64+0x3f/0xe0 |
| entry_SYSCALL_64_after_hwframe+0x63/0x6b |
| ---[ end trace 0000000000000000 ]--- |
| |
| [CAUSE] |
| During create_subvol(), after inserting root item for the newly created |
| subvolume, we would trigger btrfs_get_new_fs_root() to get the |
| btrfs_root of that subvolume. |
| |
| The idea here is, we have preallocated an anonymous device number for |
| the subvolume, thus we can assign it to the new subvolume. |
| |
| But there is really nothing preventing things like backref walk to read |
| the new subvolume. |
| If that happens before we call btrfs_get_new_fs_root(), the subvolume |
| would be read out, with a new anonymous device number assigned already. |
| |
| In that case, we would trigger ASSERT(), as we really expect no one to |
| read out that subvolume (which is not yet accessible from the fs). |
| But things like backref walk is still possible to trigger the read on |
| the subvolume. |
| |
| Thus our assumption on the ASSERT() is not correct in the first place. |
| |
| [FIX] |
| Fix it by removing the ASSERT(), and just free the @anon_dev, reset it |
| to 0, and continue. |
| |
| If the subvolume tree is read out by something else, it should have |
| already get a new anon_dev assigned thus we only need to free the |
| preallocated one. |
| |
| The Linux kernel CVE team has assigned CVE-2024-26727 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.9 with commit 2dfb1e43f57dd3aeaa66f7cf05d068db2d4c8788 and fixed in 5.10.210 with commit 3f5d47eb163bceb1b9e613c9003bae5fefc0046f |
| Issue introduced in 5.9 with commit 2dfb1e43f57dd3aeaa66f7cf05d068db2d4c8788 and fixed in 5.15.149 with commit e31546b0f34af21738c4ceac47d662c00ee6382f |
| Issue introduced in 5.9 with commit 2dfb1e43f57dd3aeaa66f7cf05d068db2d4c8788 and fixed in 6.1.79 with commit 66b317a2fc45b2ef66527ee3f8fa08fb5beab88d |
| Issue introduced in 5.9 with commit 2dfb1e43f57dd3aeaa66f7cf05d068db2d4c8788 and fixed in 6.6.18 with commit 833775656d447c545133a744a0ed1e189ce61430 |
| Issue introduced in 5.9 with commit 2dfb1e43f57dd3aeaa66f7cf05d068db2d4c8788 and fixed in 6.7.6 with commit 5a172344bfdabb46458e03708735d7b1a918c468 |
| Issue introduced in 5.9 with commit 2dfb1e43f57dd3aeaa66f7cf05d068db2d4c8788 and fixed in 6.8 with commit e03ee2fe873eb68c1f9ba5112fee70303ebf9dfb |
| Issue introduced in 5.8.3 with commit 917d608fe375041eb7f29befa6a6d7fd3cf32dde |
| |
| 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-2024-26727 |
| 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/btrfs/disk-io.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/3f5d47eb163bceb1b9e613c9003bae5fefc0046f |
| https://git.kernel.org/stable/c/e31546b0f34af21738c4ceac47d662c00ee6382f |
| https://git.kernel.org/stable/c/66b317a2fc45b2ef66527ee3f8fa08fb5beab88d |
| https://git.kernel.org/stable/c/833775656d447c545133a744a0ed1e189ce61430 |
| https://git.kernel.org/stable/c/5a172344bfdabb46458e03708735d7b1a918c468 |
| https://git.kernel.org/stable/c/e03ee2fe873eb68c1f9ba5112fee70303ebf9dfb |
