| Message ID | 20171211132806.16962-1-thiago.becker@gmail.com (mailing list archive) |
|---|---|
| State | Rejected, archived |
| Headers | show |
On Mon, Dec 11, 2017 at 11:28:06AM -0200, Thiago Rafael Becker wrote: > +++ b/fs/nfsd/auth.c > @@ -60,6 +60,9 @@ int nfsd_setuser(struct svc_rqst *rqstp, struct svc_export *exp) > gi->gid[i] = exp->ex_anon_gid; > else > gi->gid[i] = rqgi->gid[i]; > + > + /* Should be race free as long as each thread allocates a new gi */ > + groups_sort(gi); > } Overlong line. Would recommend: /* Each thread has its own gi, so no race */ > +++ b/kernel/groups.c > @@ -86,11 +86,13 @@ static int gid_cmp(const void *_a, const void *_b) > return gid_gt(a, b) - gid_lt(a, b); > } > > -static void groups_sort(struct group_info *group_info) > +void groups_sort(struct group_info *group_info) > { > sort(group_info->gid, group_info->ngroups, sizeof(*group_info->gid), > gid_cmp, NULL); > } > +EXPORT_SYMBOL(groups_sort); > + > Spurious extra line > diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c > index 740b67d..7154dab 100644 > --- a/net/sunrpc/svcauth_unix.c > +++ b/net/sunrpc/svcauth_unix.c > @@ -520,6 +520,12 @@ static int unix_gid_parse(struct cache_detail *cd, > ug.gi->gid[i] = kgid; > } > > + /* Sort the groups before inserting this entry > + * into the cache to avoid future corrutpions > + * by multiple simultaneous attempts to sort this > + * entry. > + */ > + groups_sort(ug.gi); > ugp = unix_gid_lookup(cd, uid); > if (ugp) { > struct cache_head *ch; Why comment this call and not the other ones? I appreciate this is the call-site where you discovered the bug, but that's not going to make it special to someone who's reading this code in ten years time. I would leave this comment out entirely; it's just the new way we do things. I can't find anything else to critique; nice job. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/s390/kernel/compat_linux.c b/arch/s390/kernel/compat_linux.c index f04db37..59eea9c 100644 --- a/arch/s390/kernel/compat_linux.c +++ b/arch/s390/kernel/compat_linux.c @@ -263,6 +263,7 @@ COMPAT_SYSCALL_DEFINE2(s390_setgroups16, int, gidsetsize, u16 __user *, grouplis return retval; } + groups_sort(group_info); retval = set_current_groups(group_info); put_group_info(group_info); diff --git a/fs/nfsd/auth.c b/fs/nfsd/auth.c index 697f8ae..7b5099b 100644 --- a/fs/nfsd/auth.c +++ b/fs/nfsd/auth.c @@ -60,6 +60,9 @@ int nfsd_setuser(struct svc_rqst *rqstp, struct svc_export *exp) gi->gid[i] = exp->ex_anon_gid; else gi->gid[i] = rqgi->gid[i]; + + /* Should be race free as long as each thread allocates a new gi */ + groups_sort(gi); } } else { gi = get_group_info(rqgi); diff --git a/include/linux/cred.h b/include/linux/cred.h index 099058e..6312865 100644 --- a/include/linux/cred.h +++ b/include/linux/cred.h @@ -83,6 +83,7 @@ extern int set_current_groups(struct group_info *); extern void set_groups(struct cred *, struct group_info *); extern int groups_search(const struct group_info *, kgid_t); extern bool may_setgroups(void); +extern void groups_sort(struct group_info *); /* * The security context of a task diff --git a/kernel/groups.c b/kernel/groups.c index e357bc8..8620ad3 100644 --- a/kernel/groups.c +++ b/kernel/groups.c @@ -86,11 +86,13 @@ static int gid_cmp(const void *_a, const void *_b) return gid_gt(a, b) - gid_lt(a, b); } -static void groups_sort(struct group_info *group_info) +void groups_sort(struct group_info *group_info) { sort(group_info->gid, group_info->ngroups, sizeof(*group_info->gid), gid_cmp, NULL); } +EXPORT_SYMBOL(groups_sort); + /* a simple bsearch */ int groups_search(const struct group_info *group_info, kgid_t grp) @@ -122,7 +124,6 @@ int groups_search(const struct group_info *group_info, kgid_t grp) void set_groups(struct cred *new, struct group_info *group_info) { put_group_info(new->group_info); - groups_sort(group_info); get_group_info(group_info); new->group_info = group_info; } @@ -206,6 +207,7 @@ SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist) return retval; } + groups_sort(group_info); retval = set_current_groups(group_info); put_group_info(group_info); diff --git a/kernel/uid16.c b/kernel/uid16.c index ce74a49..ef1da2a 100644 --- a/kernel/uid16.c +++ b/kernel/uid16.c @@ -192,6 +192,7 @@ SYSCALL_DEFINE2(setgroups16, int, gidsetsize, old_gid_t __user *, grouplist) return retval; } + groups_sort(group_info); retval = set_current_groups(group_info); put_group_info(group_info); diff --git a/net/sunrpc/auth_gss/gss_rpc_xdr.c b/net/sunrpc/auth_gss/gss_rpc_xdr.c index c4778ca..444380f 100644 --- a/net/sunrpc/auth_gss/gss_rpc_xdr.c +++ b/net/sunrpc/auth_gss/gss_rpc_xdr.c @@ -231,6 +231,7 @@ static int gssx_dec_linux_creds(struct xdr_stream *xdr, goto out_free_groups; creds->cr_group_info->gid[i] = kgid; } + groups_sort(creds->cr_group_info); return 0; out_free_groups: diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c index 5dd4e6c..2653119 100644 --- a/net/sunrpc/auth_gss/svcauth_gss.c +++ b/net/sunrpc/auth_gss/svcauth_gss.c @@ -481,6 +481,7 @@ static int rsc_parse(struct cache_detail *cd, goto out; rsci.cred.cr_group_info->gid[i] = kgid; } + groups_sort(rsci.cred.cr_group_info); /* mech name */ len = qword_get(&mesg, buf, mlen); diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c index 740b67d..7154dab 100644 --- a/net/sunrpc/svcauth_unix.c +++ b/net/sunrpc/svcauth_unix.c @@ -520,6 +520,12 @@ static int unix_gid_parse(struct cache_detail *cd, ug.gi->gid[i] = kgid; } + /* Sort the groups before inserting this entry + * into the cache to avoid future corrutpions + * by multiple simultaneous attempts to sort this + * entry. + */ + groups_sort(ug.gi); ugp = unix_gid_lookup(cd, uid); if (ugp) { struct cache_head *ch; @@ -819,6 +825,7 @@ svcauth_unix_accept(struct svc_rqst *rqstp, __be32 *authp) kgid_t kgid = make_kgid(&init_user_ns, svc_getnl(argv)); cred->cr_group_info->gid[i] = kgid; } + groups_sort(cred->cr_group_info); if (svc_getu32(argv) != htonl(RPC_AUTH_NULL) || svc_getu32(argv) != 0) { *authp = rpc_autherr_badverf; return SVC_DENIED;
In testing, we found that nfsd threads may call set_groups in parallel for the same entry cached in auth.unix.gid, racing in the call of groups_sort, corrupting the groups for that entry and leading to permission denials for the client. This patch: - Make groups_sort globally visible. - Move the call to groups_sort to the modifiers of group_info - Remove the call to groups_sort from set_groups Signed-off-by: Thiago Rafael Becker <thiago.becker@gmail.com> --- arch/s390/kernel/compat_linux.c | 1 + fs/nfsd/auth.c | 3 +++ include/linux/cred.h | 1 + kernel/groups.c | 6 ++++-- kernel/uid16.c | 1 + net/sunrpc/auth_gss/gss_rpc_xdr.c | 1 + net/sunrpc/auth_gss/svcauth_gss.c | 1 + net/sunrpc/svcauth_unix.c | 7 +++++++ 8 files changed, 19 insertions(+), 2 deletions(-)