On Sat, 2 Apr 2011 13:24:48 -0500
shirishpargaonkar@xxxxxxxxx wrote:
> From: Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx>
>
> rb tree search and insertion routines.
>
> A SID which needs to be mapped, is looked up in one of the rb trees
> depending whether SID is either owner or group SID.
> If found in the tree, a (mapped) id from that node is assigned to
> uid or gid as appropriate. If unmapped, an upcall is attempted to
> map the SID to an id. If upcall is successful, node is marked as
> mapped. If upcall fails, node stays marked as unmapped and a mapping
> is attempted again only after an arbitrary time period has passed.
>
> To map a SID, which can be either a Owner SID or a Group SID, key
> description starts with the string "os" or "gs" followed by SID converted
> to a string. Without "os" or "gs", cifs.upcall does not know whether
> SID needs to be mapped to either an uid or a gid.
>
> Nodes in rb tree as fields to prevent multiple upcalls for
> a SID. Adding and removing nodes is done within global locks.
> shrinker routine does not prune a node if mapping for that node
> is either pending or or node was recently created (before timeout
> period expires and node could be purged). The timeout period should
> be long enough at least for an upcall to return back to cifs.
>
> For now, cifs.upcall is only used to map a SID to an id (uid or gid) but
> it would be used to obtain an SID (string) for an id.
>
>
> Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx>
> ---
> fs/cifs/cifsacl.c | 300 ++++++++++++++++++++++++++++++++++++++++++++++++-----
> fs/cifs/cifsacl.h | 24 +++++
> 2 files changed, 300 insertions(+), 24 deletions(-)
>
> diff --git a/fs/cifs/cifsacl.c b/fs/cifs/cifsacl.c
> index c60bb90..b7489a0 100644
> --- a/fs/cifs/cifsacl.c
> +++ b/fs/cifs/cifsacl.c
> @@ -54,7 +54,30 @@ static const struct cifs_sid sid_authusers = {
> /* group users */
> static const struct cifs_sid sid_user = {1, 2 , {0, 0, 0, 0, 0, 5}, {} };
>
> -static const struct cred *root_cred;
> +const struct cred *root_cred;
> +
> +static void
> +shrink_idmap_tree(struct rb_root *root, int nr_to_scan, int *nr_rem,
> + int *nr_del)
> +{
> + struct rb_node *node;
> + struct rb_node *tmp;
> + struct cifs_sid_id *psidid;
> +
> + node = rb_first(root);
> + while (node) {
> + tmp = node;
> + node = rb_next(tmp);
> + psidid = rb_entry(tmp, struct cifs_sid_id, rbnode);
> + if (time_after(psidid->time + SID_MAP_EXPIRE, jiffies) ||
> + (nr_to_scan == 0) || (*nr_del == nr_to_scan))
> + ++(*nr_rem);
> + else {
> + rb_erase(tmp, root);
> + ++(*nr_del);
> + }
> + }
> +}
>
> /*
> * Run idmap cache shrinker.
> @@ -62,9 +85,21 @@ static const struct cred *root_cred;
> static int
> cifs_idmap_shrinker(struct shrinker *shrink, int nr_to_scan, gfp_t gfp_mask)
> {
> - /* Use a pruning scheme in a subsequent patch instead */
> - cifs_destroy_idmaptrees();
> - return 0;
> + int nr_del = 0;
> + int nr_rem = 0;
> + struct rb_root *root;
> +
> + root = &uidtree;
> + spin_lock(&siduidlock);
> + shrink_idmap_tree(root, nr_to_scan, &nr_rem, &nr_del);
> + spin_unlock(&siduidlock);
> +
> + root = &gidtree;
> + spin_lock(&sidgidlock);
> + shrink_idmap_tree(root, nr_to_scan, &nr_rem, &nr_del);
> + spin_unlock(&sidgidlock);
> +
> + return nr_rem;
> }
>
> static struct shrinker cifs_shrinker = {
> @@ -92,7 +127,6 @@ cifs_idmap_key_destroy(struct key *key)
> kfree(key->payload.data);
> }
>
> -static
> struct key_type cifs_idmap_key_type = {
> .name = "cifs.cifs_idmap",
> .instantiate = cifs_idmap_key_instantiate,
> @@ -101,6 +135,198 @@ struct key_type cifs_idmap_key_type = {
> .match = user_match,
> };
>
> +static void
> +sid_to_str(struct cifs_sid *sidptr, char *sidstr)
> +{
> + int i;
> + unsigned long saval;
> + char *strptr;
> +
> + strptr = sidstr;
> +
> + sprintf(strptr, "%s", "S");
> + strptr = sidstr + strlen(sidstr);
> +
> + sprintf(strptr, "-%d", sidptr->revision);
> + strptr = sidstr + strlen(sidstr);
> +
> + for (i = 0; i < 6; ++i) {
> + if (sidptr->authority[i]) {
> + sprintf(strptr, "-%d", sidptr->authority[i]);
> + strptr = sidstr + strlen(sidstr);
> + }
> + }
> +
> + for (i = 0; i < sidptr->num_subauth; ++i) {
> + saval = le32_to_cpu(sidptr->sub_auth[i]);
> + sprintf(strptr, "-%ld", saval);
> + strptr = sidstr + strlen(sidstr);
> + }
> +}
> +
> +static void
> +id_rb_insert(struct rb_root *root, struct cifs_sid *sidptr,
> + struct cifs_sid_id **psidid, char *typestr)
> +{
> + int rc;
> + char *strptr;
> + struct rb_node *node = root->rb_node;
> + struct rb_node *parent = NULL;
> + struct rb_node **linkto = &(root->rb_node);
> + struct cifs_sid_id *lsidid;
> +
> + while (node) {
> + lsidid = rb_entry(node, struct cifs_sid_id, rbnode);
> + parent = node;
> + rc = compare_sids(sidptr, &((lsidid)->sid));
> + if (rc > 0) {
> + linkto = &(node->rb_left);
> + node = node->rb_left;
> + } else if (rc < 0) {
> + linkto = &(node->rb_right);
> + node = node->rb_right;
> + }
> + }
> +
> + memcpy(&(*psidid)->sid, sidptr, sizeof(struct cifs_sid));
> + (*psidid)->time = jiffies;
> + (*psidid)->retry = jiffies - (SID_MAP_RETRY + 1);
> +
> + sprintf((*psidid)->sidstr, "%s", typestr);
> + strptr = (*psidid)->sidstr + strlen((*psidid)->sidstr);
> + sid_to_str(&(*psidid)->sid, strptr);
> +
> + clear_bit(SID_ID_PENDING, &(*psidid)->state);
> + clear_bit(SID_ID_MAPPED, &(*psidid)->state);
> +
> + rb_link_node(&(*psidid)->rbnode, parent, linkto);
> + rb_insert_color(&(*psidid)->rbnode, root);
> +}
> +
> +static struct cifs_sid_id *
> +id_rb_search(struct rb_root *root, struct cifs_sid *sidptr)
> +{
> + int rc;
> + struct rb_node *node = root->rb_node;
> + struct rb_node *parent = NULL;
> + struct rb_node **linkto = &(root->rb_node);
> + struct cifs_sid_id *lsidid;
> +
> + while (node) {
> + lsidid = rb_entry(node, struct cifs_sid_id, rbnode);
> + parent = node;
> + rc = compare_sids(sidptr, &((lsidid)->sid));
> + if (rc > 0) {
> + linkto = &(node->rb_left);
> + node = node->rb_left;
> + } else if (rc < 0) {
> + linkto = &(node->rb_right);
> + node = node->rb_right;
> + } else /* node found */
> + return lsidid;
> + }
> +
> + return NULL;
> +}
> +
> +static int
> +sidid_pending_wait(void *unused)
> +{
> + schedule();
> + return signal_pending(current) ? -ERESTARTSYS : 0;
> +}
> +
> +static int
> +sid_to_id(struct cifs_sb_info *cifs_sb, struct cifs_sid *psid,
> + struct cifs_fattr *fattr, uint sidtype)
> +{
> + int rc;
> + unsigned long cid;
> + struct key *idkey;
> + const struct cred *saved_cred;
> + struct cifs_sid_id *psidid, *npsidid;
> + struct rb_root *cidtree;
> + spinlock_t *cidlock;
> +
> + if (sidtype == SIDOWNER) {
> + cid = cifs_sb->mnt_uid; /* default uid, in case upcall fails */
> + cidlock = &siduidlock;
> + cidtree = &uidtree;
> + } else if (sidtype == SIDGROUP) {
> + cid = cifs_sb->mnt_gid; /* default gid, in case upcall fails */
> + cidlock = &sidgidlock;
> + cidtree = &gidtree;
> + } else
> + return -ENOENT;
> +
> + spin_lock(cidlock);
> + psidid = id_rb_search(cidtree, psid);
> + spin_unlock(cidlock);
> +
> + if (!psidid) { /* node does not exist, allocate one & attempt adding */
> + npsidid = kzalloc(sizeof(struct cifs_sid_id), GFP_KERNEL);
> + if (!npsidid)
> + return -ENOMEM;
> +
> + npsidid->sidstr = kmalloc(SIDLEN, GFP_KERNEL);
> + if (!npsidid->sidstr) {
> + kfree(npsidid);
> + return -ENOMEM;
> + }
> +
> + spin_lock(cidlock);
> + psidid = id_rb_search(cidtree, psid);
> + if (psidid) { /* node happened to get inserted meanwhile */
> + spin_unlock(cidlock);
> + kfree(npsidid->sidstr);
> + kfree(npsidid);
> + } else {
> + psidid = npsidid;
> + id_rb_insert(cidtree, psid, &psidid,
> + sidtype == SIDOWNER ? "os:" : "gs:");
> + spin_unlock(cidlock);
> + }
> + }
> +
> + if (test_bit(SID_ID_MAPPED, &psidid->state))
> + goto sid_to_id_out; /* SID mapped */
> + if (time_after(psidid->retry + SID_MAP_RETRY, jiffies))
> + goto sid_to_id_out; /* wait before re-attempting SID mapping */
> + if (!test_and_set_bit(SID_ID_PENDING, &psidid->state)) {
> + saved_cred = override_creds(root_cred);
> + idkey = request_key(&cifs_idmap_key_type, psidid->sidstr, "");
> + if (IS_ERR(idkey)) {
> + psidid->id = cid;
> + psidid->retry = jiffies;
> + cFYI(1, "%s: Can't map SID to an id", __func__);
> + } else {
> + psidid->id = *(unsigned long *)idkey->payload.value;
> + set_bit(SID_ID_MAPPED, &psidid->state);
> + key_put(idkey);
> + kfree(psidid->sidstr);
> + }
This patch looks much better overall. One problem though...
You're passing in the cifs_sb here, primarily to get the
mnt_uid and mnt_gid (right?). The cache itself though is
global. So, if I have two mounts with different mnt_uid/mnt_gid
then I can end up upcalling for a uid that fails. Then I can
end up accessing that same cached entry from a different mount,
but it's mapped to the mnt_uid for the *other* superblock.
I think it would be better to not store the mnt_uid in the
entry in the event that the upcall fails, and instead just set
the fattr->cf_uid/cf_gid to the mnt_uid/mnt_gid when you end up
with an unmapped entry.
> + revert_creds(saved_cred);
> + clear_bit(SID_ID_PENDING, &psidid->state);
> + wake_up_bit(&psidid->state, SID_ID_PENDING);
> + } else {
> + rc = wait_on_bit(&psidid->state, SID_ID_PENDING,
> + sidid_pending_wait, TASK_INTERRUPTIBLE);
> + if (rc) {
> + cFYI(1, "%s: sidid_pending_wait interrupted %d",
> + __func__, rc);
> + return rc;
> + }
> + }
> +
> +sid_to_id_out:
> + if (sidtype == SIDOWNER)
> + fattr->cf_uid = psidid->id;
> + else
> + fattr->cf_gid = psidid->id;
> +
> + return 0;
> +}
> +
> int
> init_cifs_idmap(void)
> {
> @@ -242,16 +468,24 @@ int compare_sids(const struct cifs_sid *ctsid, const struct cifs_sid *cwsid)
> int num_subauth, num_sat, num_saw;
>
> if ((!ctsid) || (!cwsid))
> - return 0;
> + return 1;
>
> /* compare the revision */
> - if (ctsid->revision != cwsid->revision)
> - return 0;
> + if (ctsid->revision != cwsid->revision) {
> + if (ctsid->revision > cwsid->revision)
> + return 1;
> + else
> + return -1;
> + }
>
> /* compare all of the six auth values */
> for (i = 0; i < 6; ++i) {
> - if (ctsid->authority[i] != cwsid->authority[i])
> - return 0;
> + if (ctsid->authority[i] != cwsid->authority[i]) {
> + if (ctsid->authority[i] > cwsid->authority[i])
> + return 1;
> + else
> + return -1;
> + }
> }
>
> /* compare all of the subauth values if any */
> @@ -260,12 +494,16 @@ int compare_sids(const struct cifs_sid *ctsid, const struct cifs_sid *cwsid)
> num_subauth = num_sat < num_saw ? num_sat : num_saw;
> if (num_subauth) {
> for (i = 0; i < num_subauth; ++i) {
> - if (ctsid->sub_auth[i] != cwsid->sub_auth[i])
> - return 0;
> + if (ctsid->sub_auth[i] != cwsid->sub_auth[i]) {
> + if (ctsid->sub_auth[i] > cwsid->sub_auth[i])
> + return 1;
> + else
> + return -1;
> + }
> }
> }
>
> - return 1; /* sids compare/match */
> + return 0; /* sids compare/match */
> }
>
>
> @@ -520,22 +758,22 @@ static void parse_dacl(struct cifs_acl *pdacl, char *end_of_acl,
> #ifdef CONFIG_CIFS_DEBUG2
> dump_ace(ppace[i], end_of_acl);
> #endif
> - if (compare_sids(&(ppace[i]->sid), pownersid))
> + if (compare_sids(&(ppace[i]->sid), pownersid) == 0)
> access_flags_to_mode(ppace[i]->access_req,
> ppace[i]->type,
> &fattr->cf_mode,
> &user_mask);
> - if (compare_sids(&(ppace[i]->sid), pgrpsid))
> + if (compare_sids(&(ppace[i]->sid), pgrpsid) == 0)
> access_flags_to_mode(ppace[i]->access_req,
> ppace[i]->type,
> &fattr->cf_mode,
> &group_mask);
> - if (compare_sids(&(ppace[i]->sid), &sid_everyone))
> + if (compare_sids(&(ppace[i]->sid), &sid_everyone) == 0)
> access_flags_to_mode(ppace[i]->access_req,
> ppace[i]->type,
> &fattr->cf_mode,
> &other_mask);
> - if (compare_sids(&(ppace[i]->sid), &sid_authusers))
> + if (compare_sids(&(ppace[i]->sid), &sid_authusers) == 0)
> access_flags_to_mode(ppace[i]->access_req,
> ppace[i]->type,
> &fattr->cf_mode,
> @@ -613,10 +851,10 @@ static int parse_sid(struct cifs_sid *psid, char *end_of_acl)
>
>
> /* Convert CIFS ACL to POSIX form */
> -static int parse_sec_desc(struct cifs_ntsd *pntsd, int acl_len,
> - struct cifs_fattr *fattr)
> +static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
> + struct cifs_ntsd *pntsd, int acl_len, struct cifs_fattr *fattr)
> {
> - int rc;
> + int rc = 0;
> struct cifs_sid *owner_sid_ptr, *group_sid_ptr;
> struct cifs_acl *dacl_ptr; /* no need for SACL ptr */
> char *end_of_acl = ((char *)pntsd) + acl_len;
> @@ -638,12 +876,26 @@ static int parse_sec_desc(struct cifs_ntsd *pntsd, int acl_len,
> le32_to_cpu(pntsd->sacloffset), dacloffset);
> /* cifs_dump_mem("owner_sid: ", owner_sid_ptr, 64); */
> rc = parse_sid(owner_sid_ptr, end_of_acl);
> - if (rc)
> + if (rc) {
> + cFYI(1, "%s: Error %d parsing Owner SID", __func__, rc);
> + return rc;
> + }
> + rc = sid_to_id(cifs_sb, owner_sid_ptr, fattr, SIDOWNER);
> + if (rc) {
> + cFYI(1, "%s: Error %d mapping Owner SID to uid", __func__, rc);
> return rc;
> + }
>
> rc = parse_sid(group_sid_ptr, end_of_acl);
> - if (rc)
> + if (rc) {
> + cFYI(1, "%s: Error %d mapping Owner SID to gid", __func__, rc);
> return rc;
> + }
> + rc = sid_to_id(cifs_sb, group_sid_ptr, fattr, SIDGROUP);
> + if (rc) {
> + cFYI(1, "%s: Error %d mapping Group SID to gid", __func__, rc);
> + return rc;
> + }
>
> if (dacloffset)
> parse_dacl(dacl_ptr, end_of_acl, owner_sid_ptr,
> @@ -658,7 +910,7 @@ static int parse_sec_desc(struct cifs_ntsd *pntsd, int acl_len,
> memcpy((void *)(&(cifscred->gsid)), (void *)group_sid_ptr,
> sizeof(struct cifs_sid)); */
>
> - return 0;
> + return rc;
> }
>
>
> @@ -865,7 +1117,7 @@ cifs_acl_to_fattr(struct cifs_sb_info *cifs_sb, struct cifs_fattr *fattr,
> rc = PTR_ERR(pntsd);
> cERROR(1, "%s: error %d getting sec desc", __func__, rc);
> } else {
> - rc = parse_sec_desc(pntsd, acllen, fattr);
> + rc = parse_sec_desc(cifs_sb, pntsd, acllen, fattr);
> kfree(pntsd);
> if (rc)
> cERROR(1, "parse sec desc failed rc = %d", rc);
> diff --git a/fs/cifs/cifsacl.h b/fs/cifs/cifsacl.h
> index 025e943..7f25b44 100644
> --- a/fs/cifs/cifsacl.h
> +++ b/fs/cifs/cifsacl.h
> @@ -39,6 +39,15 @@
> #define ACCESS_ALLOWED 0
> #define ACCESS_DENIED 1
>
> +#define SIDOWNER 1
> +#define SIDGROUP 2
> +#define SIDLEN 150 /* S- 1 revision- 6 authorities- max 5 sub authorities */
> +
> +#define SID_ID_MAPPED 0
> +#define SID_ID_PENDING 1
> +#define SID_MAP_EXPIRE 1000 /* enough for an upcall to return? */
> +#define SID_MAP_RETRY 1000 /* wait for next attempt to map sid */
> +
> struct cifs_ntsd {
> __le16 revision; /* revision level */
> __le16 type;
> @@ -74,6 +83,21 @@ struct cifs_wksid {
> char sidname[SIDNAMELENGTH];
> } __attribute__((packed));
>
> +struct cifs_sid_id {
> + unsigned long id;
> + unsigned long time;
> + unsigned long retry;
> + unsigned long state;
> + char *sidstr;
> + struct rb_node rbnode;
> + struct cifs_sid sid;
> +};
> +
> +#ifdef __KERNEL__
> +extern struct key_type cifs_idmap_key_type;
> +extern const struct cred *root_cred;
> +#endif /* KERNEL */
> +
> extern int match_sid(struct cifs_sid *);
> extern int compare_sids(const struct cifs_sid *, const struct cifs_sid *);
>
--
Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
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