Description
In the Linux kernel, the following vulnerability has been resolved: nfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL deref When CONFIG_NFSD_V4_2_INTER_SSC is enabled, nfsd4_putfh() can return success with fh_dentry and fh_export both NULL if fh_verify() returns nfserr_stale and putfh->no_verify is true. The NFSD4_FH_FOREIGN flag is set, but the compound dispatch loop only uses this flag to bypass the nfserr_nofilehandle check -- it does not prevent subsequent ops from running with a NULL fh_dentry. A remote client can exploit this by crafting a COMPOUND that includes an inter-SSC COPY (which causes check_if_stalefh_allowed() to set no_verify=true on the saved PUTFH) with an additional op inserted between the source PUTFH and SAVEFH. For example, SETATTR calls fh_want_write() which dereferences fh_export->ex_path.mnt without calling fh_verify() first, causing a NULL pointer dereference in the nfsd kthread. Fix this by gating the dispatch loop: when NFSD4_FH_FOREIGN is set and fh_dentry is NULL, only OP_SAVEFH (needed for the inter-SSC flow) and ops with ALLOWED_WITHOUT_FH (which don't need a resolved filehandle) may proceed. All other ops receive nfserr_stale, per RFC 7862 Section 15.2.3 which specifies that foreign filehandle validation is deferred to the consuming operation and NFS4ERR_STALE returned at that point.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
b9e8638e3d9ed8334f1f7071e081860aac37e83e to < ffdc844e673d2bcb2af8c8c3eef8cdea59d0bf32affectedb9e8638e3d9ed8334f1f7071e081860aac37e83e to < 00c84f4eec715e501efc080a5670114189e42507affectedb9e8638e3d9ed8334f1f7071e081860aac37e83e to < 2d9846fd1c767920fddd4bde30eb35cd2969df13affectedb9e8638e3d9ed8334f1f7071e081860aac37e83e to < 977e6f006a7a3ffc4216ae6034f768f8de6fd138affectedb9e8638e3d9ed8334f1f7071e081860aac37e83e to < 35f248bd40b47b229d4999581df45b97daadd977affectedb9e8638e3d9ed8334f1f7071e081860aac37e83e to < 311f7d926630940650447cbd1c932b076b40a6c4affectedb9e8638e3d9ed8334f1f7071e081860aac37e83e to < bf4d338dc8625d70c7f2cb0657d66851a7ac9154affectedb9e8638e3d9ed8334f1f7071e081860aac37e83e to < c59738a00aa51b16adc1b5ceb7c80877168efb4daffected
Linux Linux
Default version status: affected
5.6affected0 to < 5.6unaffected5.10.270 to ≤ 5.10.*unaffected5.15.221 to ≤ 5.15.*unaffected6.1.188 to ≤ 6.1.*unaffected6.6.157 to ≤ 6.6.*unaffected6.12.109 to ≤ 6.12.*unaffected6.18.50 to ≤ 6.18.*unaffected7.2.4 to ≤ 7.2.*unaffected7.3 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/ffdc844e673d2bcb2af8c8c3eef8cdea59d0bf32 ↗
- https://git.kernel.org/stable/c/00c84f4eec715e501efc080a5670114189e42507 ↗
- https://git.kernel.org/stable/c/2d9846fd1c767920fddd4bde30eb35cd2969df13 ↗
- https://git.kernel.org/stable/c/977e6f006a7a3ffc4216ae6034f768f8de6fd138 ↗
- https://git.kernel.org/stable/c/35f248bd40b47b229d4999581df45b97daadd977 ↗
- https://git.kernel.org/stable/c/311f7d926630940650447cbd1c932b076b40a6c4 ↗
- https://git.kernel.org/stable/c/bf4d338dc8625d70c7f2cb0657d66851a7ac9154 ↗
- https://git.kernel.org/stable/c/c59738a00aa51b16adc1b5ceb7c80877168efb4d ↗