The branch main has been updated by rmacklem: URL: https://cgit.FreeBSD.org/src/commit/?id=1cedb4ea1a790f976ec6211c938dfaa23874b497
commit 1cedb4ea1a790f976ec6211c938dfaa23874b497 Author: Rick Macklem <[email protected]> AuthorDate: 2022-02-25 15:27:03 +0000 Commit: Rick Macklem <[email protected]> CommitDate: 2022-02-25 15:27:03 +0000 nfscl: Fix a use after free in nfscl_cleanupkext() ler@, markj@ reported a use after free in nfscl_cleanupkext(). They also provided two possible causes: - In nfscl_cleanup_common(), "own" is the owner string owp->nfsow_owner. If we free that particular owner structure, than in subsequent comparisons "own" will point to freed memory. - nfscl_cleanup_common() can free more than one owner, so the use of LIST_FOREACH_SAFE() in nfscl_cleanupkext() is not sufficient. I also believe there is a 3rd: - If nfscl_freeopenowner() or nfscl_freelockowner() is called without the NFSCLSTATE mutex held, this could race with nfscl_cleanupkext(). This could happen when the exclusive lock is held on the client, such as when delegations are being returned or when recovering from NFSERR_EXPIRED. This patch fixes them as follows: 1 - Copy the owner string to a local variable before the nfscl_cleanup_common() call. 2 - Modify nfscl_cleanup_common() so that it will never free more than the first matching element. Normally there should only be one element in each list with a matching open/lock owner anyhow (but there might be a bug that results in a duplicate). This should guarantee that the FOREACH_SAFE loops in nfscl_cleanupkext() are adequate. 3 - Acquire the NFSCLSTATE mutex in nfscl_freeopenowner() and nfscl_freelockowner(), if it is not already held. This serializes all of these calls with the ones done in nfscl_cleanup_common(). Reported by: ler Reviewed by: markj Tested by: cy MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D34334 --- sys/fs/nfsclient/nfs_clstate.c | 48 ++++++++++++++++++++++++++++++++++++------ 1 file changed, 42 insertions(+), 6 deletions(-) diff --git a/sys/fs/nfsclient/nfs_clstate.c b/sys/fs/nfsclient/nfs_clstate.c index 5262986645cd..7ee98aa901d8 100644 --- a/sys/fs/nfsclient/nfs_clstate.c +++ b/sys/fs/nfsclient/nfs_clstate.c @@ -1642,8 +1642,22 @@ nfscl_expireopen(struct nfsclclient *clp, struct nfsclopen *op, static void nfscl_freeopenowner(struct nfsclowner *owp, int local) { + int owned; + /* + * Make sure the NFSCLSTATE mutex is held, to avoid races with + * calls in nfscl_renewthread() that do not hold a reference + * count on the nfsclclient and just the mutex. + * The mutex will not be held for calls done with the exclusive + * nfsclclient lock held, in particular, nfscl_hasexpired() + * and nfscl_recalldeleg() might do this. + */ + owned = mtx_owned(NFSCLSTATEMUTEXPTR); + if (owned == 0) + NFSLOCKCLSTATE(); LIST_REMOVE(owp, nfsow_list); + if (owned == 0) + NFSUNLOCKCLSTATE(); free(owp, M_NFSCLOWNER); if (local) nfsstatsv1.cllocalopenowners--; @@ -1658,8 +1672,22 @@ void nfscl_freelockowner(struct nfscllockowner *lp, int local) { struct nfscllock *lop, *nlop; + int owned; + /* + * Make sure the NFSCLSTATE mutex is held, to avoid races with + * calls in nfscl_renewthread() that do not hold a reference + * count on the nfsclclient and just the mutex. + * The mutex will not be held for calls done with the exclusive + * nfsclclient lock held, in particular, nfscl_hasexpired() + * and nfscl_recalldeleg() might do this. + */ + owned = mtx_owned(NFSCLSTATEMUTEXPTR); + if (owned == 0) + NFSLOCKCLSTATE(); LIST_REMOVE(lp, nfsl_list); + if (owned == 0) + NFSUNLOCKCLSTATE(); LIST_FOREACH_SAFE(lop, &lp->nfsl_lock, nfslo_list, nlop) { nfscl_freelock(lop, local); } @@ -1849,16 +1877,17 @@ static void nfscl_cleanup_common(struct nfsclclient *clp, u_int8_t *own) { struct nfsclowner *owp, *nowp; - struct nfscllockowner *lp, *nlp; + struct nfscllockowner *lp; struct nfscldeleg *dp; /* First, get rid of local locks on delegations. */ TAILQ_FOREACH(dp, &clp->nfsc_deleg, nfsdl_list) { - LIST_FOREACH_SAFE(lp, &dp->nfsdl_lock, nfsl_list, nlp) { + LIST_FOREACH(lp, &dp->nfsdl_lock, nfsl_list) { if (!NFSBCMP(lp->nfsl_owner, own, NFSV4CL_LOCKNAMELEN)) { if ((lp->nfsl_rwlock.nfslock_lock & NFSV4LOCK_WANTED)) panic("nfscllckw"); nfscl_freelockowner(lp, 1); + break; } } } @@ -1877,6 +1906,7 @@ nfscl_cleanup_common(struct nfsclclient *clp, u_int8_t *own) nfscl_freeopenowner(owp, 0); else owp->nfsow_defunct = 1; + break; } owp = nowp; } @@ -1892,6 +1922,7 @@ nfscl_cleanupkext(struct nfsclclient *clp, struct nfscllockownerfhhead *lhp) struct nfsclopen *op; struct nfscllockowner *lp, *nlp; struct nfscldeleg *dp; + uint8_t own[NFSV4CL_LOCKNAMELEN]; /* * All the pidhash locks must be acquired, since they are sx locks @@ -1908,8 +1939,10 @@ nfscl_cleanupkext(struct nfsclclient *clp, struct nfscllockownerfhhead *lhp) nfscl_emptylockowner(lp, lhp); } } - if (nfscl_procdoesntexist(owp->nfsow_owner)) - nfscl_cleanup_common(clp, owp->nfsow_owner); + if (nfscl_procdoesntexist(owp->nfsow_owner)) { + memcpy(own, owp->nfsow_owner, NFSV4CL_LOCKNAMELEN); + nfscl_cleanup_common(clp, own); + } } /* @@ -1921,8 +1954,11 @@ nfscl_cleanupkext(struct nfsclclient *clp, struct nfscllockownerfhhead *lhp) */ TAILQ_FOREACH(dp, &clp->nfsc_deleg, nfsdl_list) { LIST_FOREACH_SAFE(lp, &dp->nfsdl_lock, nfsl_list, nlp) { - if (nfscl_procdoesntexist(lp->nfsl_owner)) - nfscl_cleanup_common(clp, lp->nfsl_owner); + if (nfscl_procdoesntexist(lp->nfsl_owner)) { + memcpy(own, lp->nfsl_owner, + NFSV4CL_LOCKNAMELEN); + nfscl_cleanup_common(clp, own); + } } } NFSUNLOCKCLSTATE();
