| 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-2023-52909: nfsd: fix handling of cached open files in nfsd4_open codepath |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| nfsd: fix handling of cached open files in nfsd4_open codepath |
| |
| Commit fb70bf124b05 ("NFSD: Instantiate a struct file when creating a |
| regular NFSv4 file") added the ability to cache an open fd over a |
| compound. There are a couple of problems with the way this currently |
| works: |
| |
| It's racy, as a newly-created nfsd_file can end up with its PENDING bit |
| cleared while the nf is hashed, and the nf_file pointer is still zeroed |
| out. Other tasks can find it in this state and they expect to see a |
| valid nf_file, and can oops if nf_file is NULL. |
| |
| Also, there is no guarantee that we'll end up creating a new nfsd_file |
| if one is already in the hash. If an extant entry is in the hash with a |
| valid nf_file, nfs4_get_vfs_file will clobber its nf_file pointer with |
| the value of op_file and the old nf_file will leak. |
| |
| Fix both issues by making a new nfsd_file_acquirei_opened variant that |
| takes an optional file pointer. If one is present when this is called, |
| we'll take a new reference to it instead of trying to open the file. If |
| the nfsd_file already has a valid nf_file, we'll just ignore the |
| optional file and pass the nfsd_file back as-is. |
| |
| Also rework the tracepoints a bit to allow for an "opened" variant and |
| don't try to avoid counting acquisitions in the case where we already |
| have a cached open file. |
| |
| The Linux kernel CVE team has assigned CVE-2023-52909 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.19 with commit fb70bf124b051d4ded4ce57511dfec6d3ebf2b43 and fixed in 6.1.7 with commit 973acfdfe90c8a4e58ade97ff0653a498531ff2e |
| Issue introduced in 5.19 with commit fb70bf124b051d4ded4ce57511dfec6d3ebf2b43 and fixed in 6.2 with commit 0b3a551fa58b4da941efeb209b3770868e2eddd7 |
| |
| 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-2023-52909 |
| 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/nfsd/filecache.c |
| fs/nfsd/filecache.h |
| fs/nfsd/nfs4state.c |
| fs/nfsd/trace.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/45c08a752982116f3287afcd1bd9c50f4fab0c28 |
| https://git.kernel.org/stable/c/0b778361998d6c6356b8d2fc7ddf025fb3224654 |
| https://git.kernel.org/stable/c/973acfdfe90c8a4e58ade97ff0653a498531ff2e |
| https://git.kernel.org/stable/c/0b3a551fa58b4da941efeb209b3770868e2eddd7 |
