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    Subject[PATCH 3.2 046/140] kernel: make groups_sort calling a responsibility group_info allocators
    3.2.100-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Thiago Rafael Becker <thiago.becker@gmail.com>

    commit bdcf0a423ea1c40bbb40e7ee483b50fc8aa3d758 upstream.

    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

    Link: http://lkml.kernel.org/r/20171211151420.18655-1-thiago.becker@gmail.com
    Signed-off-by: Thiago Rafael Becker <thiago.becker@gmail.com>
    Reviewed-by: Matthew Wilcox <mawilcox@microsoft.com>
    Reviewed-by: NeilBrown <neilb@suse.com>
    Acked-by: "J. Bruce Fields" <bfields@fieldses.org>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    [bwh: Backported to 3.2:
    - Drop change in gss_rpc_xdr.c
    - Adjust context]
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    --- a/arch/s390/kernel/compat_linux.c
    +++ b/arch/s390/kernel/compat_linux.c
    @@ -242,6 +242,7 @@ asmlinkage long sys32_setgroups16(int gi
    return retval;
    }

    + groups_sort(group_info);
    retval = set_current_groups(group_info);
    put_group_info(group_info);

    --- a/fs/nfsd/auth.c
    +++ b/fs/nfsd/auth.c
    @@ -60,6 +60,9 @@ int nfsd_setuser(struct svc_rqst *rqstp,
    GROUP_AT(gi, i) = exp->ex_anon_gid;
    else
    GROUP_AT(gi, i) = GROUP_AT(rqgi, i);
    +
    + /* Each thread allocates its own gi, no race */
    + groups_sort(gi);
    }
    } else {
    gi = get_group_info(rqgi);
    --- a/include/linux/cred.h
    +++ b/include/linux/cred.h
    @@ -67,6 +67,7 @@ extern void groups_free(struct group_inf
    extern int set_current_groups(struct group_info *);
    extern int set_groups(struct cred *, struct group_info *);
    extern int groups_search(const struct group_info *, gid_t);
    +extern void groups_sort(struct group_info *);

    /* access the groups "array" with this macro */
    #define GROUP_AT(gi, i) \
    --- a/kernel/groups.c
    +++ b/kernel/groups.c
    @@ -103,7 +103,7 @@ static int groups_from_user(struct group
    }

    /* a simple Shell sort */
    -static void groups_sort(struct group_info *group_info)
    +void groups_sort(struct group_info *group_info)
    {
    int base, max, stride;
    int gidsetsize = group_info->ngroups;
    @@ -130,6 +130,7 @@ static void groups_sort(struct group_inf
    stride /= 3;
    }
    }
    +EXPORT_SYMBOL(groups_sort);

    /* a simple bsearch */
    int groups_search(const struct group_info *group_info, gid_t grp)
    @@ -164,7 +165,6 @@ int groups_search(const struct group_inf
    int 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;
    return 0;
    @@ -247,6 +247,7 @@ SYSCALL_DEFINE2(setgroups, int, gidsetsi
    return retval;
    }

    + groups_sort(group_info);
    retval = set_current_groups(group_info);
    put_group_info(group_info);

    --- a/kernel/uid16.c
    +++ b/kernel/uid16.c
    @@ -203,6 +203,7 @@ SYSCALL_DEFINE2(setgroups16, int, gidset
    return retval;
    }

    + groups_sort(group_info);
    retval = set_current_groups(group_info);
    put_group_info(group_info);

    --- a/net/sunrpc/auth_gss/svcauth_gss.c
    +++ b/net/sunrpc/auth_gss/svcauth_gss.c
    @@ -477,6 +477,7 @@ static int rsc_parse(struct cache_detail
    goto out;
    GROUP_AT(rsci.cred.cr_group_info, i) = gid;
    }
    + groups_sort(rsci.cred.cr_group_info);

    /* mech name */
    len = qword_get(&mesg, buf, mlen);
    --- a/net/sunrpc/svcauth_unix.c
    +++ b/net/sunrpc/svcauth_unix.c
    @@ -539,6 +539,7 @@ static int unix_gid_parse(struct cache_d
    GROUP_AT(ug.gi, i) = gid;
    }

    + groups_sort(ug.gi);
    ugp = unix_gid_lookup(uid);
    if (ugp) {
    struct cache_head *ch;
    @@ -806,6 +807,7 @@ svcauth_unix_accept(struct svc_rqst *rqs
    return SVC_CLOSE;
    for (i = 0; i < slen; i++)
    GROUP_AT(cred->cr_group_info, i) = svc_getnl(argv);
    + 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;
    \
     
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