| 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-2021-47107: NFSD: Fix READDIR buffer overflow |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| NFSD: Fix READDIR buffer overflow |
| |
| If a client sends a READDIR count argument that is too small (say, |
| zero), then the buffer size calculation in the new init_dirlist |
| helper functions results in an underflow, allowing the XDR stream |
| functions to write beyond the actual buffer. |
| |
| This calculation has always been suspect. NFSD has never sanity- |
| checked the READDIR count argument, but the old entry encoders |
| managed the problem correctly. |
| |
| With the commits below, entry encoding changed, exposing the |
| underflow to the pointer arithmetic in xdr_reserve_space(). |
| |
| Modern NFS clients attempt to retrieve as much data as possible |
| for each READDIR request. Also, we have no unit tests that |
| exercise the behavior of READDIR at the lower bound of @count |
| values. Thus this case was missed during testing. |
| |
| The Linux kernel CVE team has assigned CVE-2021-47107 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.13 with commit 7f87fc2d34d475225e78b7f5c4eabb121f4282b2 and fixed in 5.15.12 with commit eabc0aab98e5218ceecd82069b0d6fdfff5ee885 |
| Issue introduced in 5.13 with commit 7f87fc2d34d475225e78b7f5c4eabb121f4282b2 and fixed in 5.16 with commit 53b1119a6e5028b125f431a0116ba73510d82a72 |
| |
| 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-2021-47107 |
| 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/nfs3proc.c |
| fs/nfsd/nfsproc.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/9e291a6a28d32545ed2fd959a8165144d1724df1 |
| https://git.kernel.org/stable/c/eabc0aab98e5218ceecd82069b0d6fdfff5ee885 |
| https://git.kernel.org/stable/c/53b1119a6e5028b125f431a0116ba73510d82a72 |
