| 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-2024-47679: vfs: fix race between evice_inodes() and find_inode()&iput() |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| vfs: fix race between evice_inodes() and find_inode()&iput() |
| |
| Hi, all |
| |
| Recently I noticed a bug[1] in btrfs, after digged it into |
| and I believe it'a race in vfs. |
| |
| Let's assume there's a inode (ie ino 261) with i_count 1 is |
| called by iput(), and there's a concurrent thread calling |
| generic_shutdown_super(). |
| |
| cpu0: cpu1: |
| iput() // i_count is 1 |
| ->spin_lock(inode) |
| ->dec i_count to 0 |
| ->iput_final() generic_shutdown_super() |
| ->__inode_add_lru() ->evict_inodes() |
| // cause some reason[2] ->if (atomic_read(inode->i_count)) continue; |
| // return before // inode 261 passed the above check |
| // list_lru_add_obj() // and then schedule out |
| ->spin_unlock() |
| // note here: the inode 261 |
| // was still at sb list and hash list, |
| // and I_FREEING|I_WILL_FREE was not been set |
| |
| btrfs_iget() |
| // after some function calls |
| ->find_inode() |
| // found the above inode 261 |
| ->spin_lock(inode) |
| // check I_FREEING|I_WILL_FREE |
| // and passed |
| ->__iget() |
| ->spin_unlock(inode) // schedule back |
| ->spin_lock(inode) |
| // check (I_NEW|I_FREEING|I_WILL_FREE) flags, |
| // passed and set I_FREEING |
| iput() ->spin_unlock(inode) |
| ->spin_lock(inode) ->evict() |
| // dec i_count to 0 |
| ->iput_final() |
| ->spin_unlock() |
| ->evict() |
| |
| Now, we have two threads simultaneously evicting |
| the same inode, which may trigger the BUG(inode->i_state & I_CLEAR) |
| statement both within clear_inode() and iput(). |
| |
| To fix the bug, recheck the inode->i_count after holding i_lock. |
| Because in the most scenarios, the first check is valid, and |
| the overhead of spin_lock() can be reduced. |
| |
| If there is any misunderstanding, please let me know, thanks. |
| |
| [1]: https://lore.kernel.org/linux-btrfs/000000000000eabe1d0619c48986@google.com/ |
| [2]: The reason might be 1. SB_ACTIVE was removed or 2. mapping_shrinkable() |
| return false when I reproduced the bug. |
| |
| The Linux kernel CVE team has assigned CVE-2024-47679 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 2.6.37 with commit 63997e98a3be68d7cec806d22bf9b02b2e1daabb and fixed in 4.19.323 with commit 6cc13a80a26e6b48f78c725c01b91987d61563ef |
| Issue introduced in 2.6.37 with commit 63997e98a3be68d7cec806d22bf9b02b2e1daabb and fixed in 5.4.285 with commit 489faddb1ae75b0e1a741fe5ca2542a2b5e794a5 |
| Issue introduced in 2.6.37 with commit 63997e98a3be68d7cec806d22bf9b02b2e1daabb and fixed in 5.10.227 with commit 47a68c75052a660e4c37de41e321582ec9496195 |
| Issue introduced in 2.6.37 with commit 63997e98a3be68d7cec806d22bf9b02b2e1daabb and fixed in 5.15.168 with commit 3721a69403291e2514d13a7c3af50a006ea1153b |
| Issue introduced in 2.6.37 with commit 63997e98a3be68d7cec806d22bf9b02b2e1daabb and fixed in 6.1.113 with commit 540fb13120c9eab3ef203f90c00c8e69f37449d1 |
| Issue introduced in 2.6.37 with commit 63997e98a3be68d7cec806d22bf9b02b2e1daabb and fixed in 6.6.54 with commit 0eed942bc65de1f93eca7bda51344290f9c573bb |
| Issue introduced in 2.6.37 with commit 63997e98a3be68d7cec806d22bf9b02b2e1daabb and fixed in 6.10.13 with commit 0f8a5b6d0dafa4f533ac82e98f8b812073a7c9d1 |
| Issue introduced in 2.6.37 with commit 63997e98a3be68d7cec806d22bf9b02b2e1daabb and fixed in 6.11.2 with commit 6c857fb12b9137fee574443385d53914356bbe11 |
| Issue introduced in 2.6.37 with commit 63997e98a3be68d7cec806d22bf9b02b2e1daabb and fixed in 6.12 with commit 88b1afbf0f6b221f6c5bb66cc80cd3b38d696687 |
| |
| 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-2024-47679 |
| 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/inode.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/6cc13a80a26e6b48f78c725c01b91987d61563ef |
| https://git.kernel.org/stable/c/489faddb1ae75b0e1a741fe5ca2542a2b5e794a5 |
| https://git.kernel.org/stable/c/47a68c75052a660e4c37de41e321582ec9496195 |
| https://git.kernel.org/stable/c/3721a69403291e2514d13a7c3af50a006ea1153b |
| https://git.kernel.org/stable/c/540fb13120c9eab3ef203f90c00c8e69f37449d1 |
| https://git.kernel.org/stable/c/0eed942bc65de1f93eca7bda51344290f9c573bb |
| https://git.kernel.org/stable/c/0f8a5b6d0dafa4f533ac82e98f8b812073a7c9d1 |
| https://git.kernel.org/stable/c/6c857fb12b9137fee574443385d53914356bbe11 |
| https://git.kernel.org/stable/c/88b1afbf0f6b221f6c5bb66cc80cd3b38d696687 |
