Description
In the Linux kernel, the following vulnerability has been resolved: nfsd: fix refcount leak in nfsd_set_fh_dentry() nfsd exports a "pseudo root filesystem" which is used by NFSv4 to find the various exported filesystems using LOOKUP requests from a known root filehandle. NFSv3 uses the MOUNT protocol to find those exported filesystems and so is not given access to the pseudo root filesystem. If a v3 (or v2) client uses a filehandle from that filesystem, nfsd_set_fh_dentry() will report an error, but still stores the export in "struct svc_fh" even though it also drops the reference (exp_put()). This means that when fh_put() is called an extra reference will be dropped which can lead to use-after-free and possible denial of service. Normal NFS usage will not provide a pseudo-root filehandle to a v3 client. This bug can only be triggered by the client synthesising an incorrect filehandle. To fix this we move the assignments to the svc_fh later, after all possible error cases have been detected.
Product status
ef7f6c4904d03ccd7478e1ac20ed75f79c4ac444 (git) before b6bc86ce3944b10b9fc181fc00c1a520a20ed965
ef7f6c4904d03ccd7478e1ac20ed75f79c4ac444 (git) before c83d7365cec5eb5ebeeee2a72e29b4ca58a7e4c2
ef7f6c4904d03ccd7478e1ac20ed75f79c4ac444 (git) before 8a7348a9ed70bda1c1f51d3f1815bcbdf9f3b38c
6.12
Any version before 6.12
6.12.59 (semver)
6.17.9 (semver)
6.18 (original_commit_for_fix)
References
git.kernel.org/...c/b6bc86ce3944b10b9fc181fc00c1a520a20ed965
git.kernel.org/...c/c83d7365cec5eb5ebeeee2a72e29b4ca58a7e4c2
git.kernel.org/...c/8a7348a9ed70bda1c1f51d3f1815bcbdf9f3b38c
