Date: Wed, 4 Jan 2017 14:43:58 +0000 (UTC) From: Edward Tomasz Napierala <trasz@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r311284 - head/sys/kern Message-ID: <201701041443.v04EhwMQ034433@repo.freebsd.org>
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Author: trasz Date: Wed Jan 4 14:43:57 2017 New Revision: 311284 URL: https://svnweb.freebsd.org/changeset/base/311284 Log: Fix bug that would result in a kernel crash in some cases involving a symlink and an autofs mount request. The crash was caused by namei() calling bcopy() with a negative length, caused by numeric underflow: in lookup(), in the relookup path, the ni_pathlen was decremented too many times. The bug was introduced in r296715. Big thanks to Alex Deiter for his help with debugging this. Reviewed by: kib@ Tested by: Alex Deiter <alex.deiter at gmail.com> MFC after: 1 month Modified: head/sys/kern/vfs_lookup.c Modified: head/sys/kern/vfs_lookup.c ============================================================================== --- head/sys/kern/vfs_lookup.c Wed Jan 4 12:50:44 2017 (r311283) +++ head/sys/kern/vfs_lookup.c Wed Jan 4 14:43:57 2017 (r311284) @@ -621,11 +621,13 @@ needs_exclusive_leaf(struct mount *mp, i int lookup(struct nameidata *ndp) { - char *cp; /* pointer into pathname argument */ + char *cp; /* pointer into pathname argument */ + char *prev_ni_next; /* saved ndp->ni_next */ struct vnode *dp = NULL; /* the directory we are searching */ struct vnode *tdp; /* saved dp */ struct mount *mp; /* mount table entry */ struct prison *pr; + size_t prev_ni_pathlen; /* saved ndp->ni_pathlen */ int docache; /* == 0 do not cache last component */ int wantparent; /* 1 => wantparent or lockparent flag */ int rdonly; /* lookup read-only flag bit */ @@ -687,7 +689,11 @@ dirloop: printf("{%s}: ", cnp->cn_nameptr); *cp = c; } #endif + prev_ni_pathlen = ndp->ni_pathlen; ndp->ni_pathlen -= cnp->cn_namelen; + KASSERT(ndp->ni_pathlen <= PATH_MAX, + ("%s: ni_pathlen underflow to %zd\n", __func__, ndp->ni_pathlen)); + prev_ni_next = ndp->ni_next; ndp->ni_next = cp; /* @@ -1008,6 +1014,8 @@ nextname: ("lookup: invalid path state.")); if (relookup) { relookup = 0; + ndp->ni_pathlen = prev_ni_pathlen; + ndp->ni_next = prev_ni_next; if (ndp->ni_dvp != dp) vput(ndp->ni_dvp); else
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