Description (CNA)
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 (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected b9e8638e3d9ed8334f1f7071e081860aac37e83e before ffdc844e673d2bcb2af8c8c3eef8cdea59d0bf32; affected b9e8638e3d9ed8334f1f7071e081860aac37e83e before 00c84f4eec715e501efc080a5670114189e42507; affected b9e8638e3d9ed8334f1f7071e081860aac37e83e before 2d9846fd1c767920fddd4bde30eb35cd2969df13; affected b9e8638e3d9ed8334f1f7071e081860aac37e83e before 977e6f006a7a3ffc4216ae6034f768f8de6fd138; affected b9e8638e3d9ed8334f1f7071e081860aac37e83e before 35f248bd40b47b229d4999581df45b97daadd977; affected b9e8638e3d9ed8334f1f7071e081860aac37e83e before 311f7d926630940650447cbd1c932b076b40a6c4; affected b9e8638e3d9ed8334f1f7071e081860aac37e83e before bf4d338dc8625d70c7f2cb0657d66851a7ac9154; affected b9e8638e3d9ed8334f1f7071e081860aac37e83e before c59738a00aa51b16adc1b5ceb7c80877168efb4d |
| Linux / Linux | affected 5.6; unaffected 0 before 5.6; unaffected 5.10.270 through 5.10.*; unaffected 5.15.221 through 5.15.*; unaffected 6.1.188 through 6.1.*; unaffected 6.6.157 through 6.6.*; unaffected 6.12.109 through 6.12.*; unaffected 6.18.50 through 6.18.*; unaffected 7.2.4 through 7.2.*; unaffected 7.3 through * |
CWE
No CWE identifiers supplied.
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