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ceph: fix potential use-after-free bug when trimming caps
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commit aaf67de upstream.

When trimming the caps and just after the 'session->s_cap_lock' is
released in ceph_iterate_session_caps() the cap maybe removed by
another thread, and when using the stale cap memory in the callbacks
it will trigger use-after-free crash.

We need to check the existence of the cap just after the 'ci->i_ceph_lock'
being acquired. And do nothing if it's already removed.

Cc: stable@vger.kernel.org
Link: https://tracker.ceph.com/issues/43272
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Luís Henriques <lhenriques@suse.de>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@lxbsz @gregkh
lxbsz authored and gregkh committed May 11, 2023
1 parent 517ddc0 commit ae6e935
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Showing 5 changed files with 62 additions and 35 deletions.
2 changes: 1 addition & 1 deletion fs/ceph/caps.c
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Original file line number Diff line number Diff line change
Expand Up @@ -431,7 +431,7 @@ void ceph_reservation_status(struct ceph_fs_client *fsc,
*
* Called with i_ceph_lock held.
*/
static struct ceph_cap *__get_cap_for_mds(struct ceph_inode_info *ci, int mds)
struct ceph_cap *__get_cap_for_mds(struct ceph_inode_info *ci, int mds)
{
struct ceph_cap *cap;
struct rb_node *n = ci->i_caps.rb_node;
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18 changes: 12 additions & 6 deletions fs/ceph/debugfs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -248,14 +248,20 @@ static int metrics_caps_show(struct seq_file *s, void *p)
return 0;
}

static int caps_show_cb(struct inode *inode, struct ceph_cap *cap, void *p)
static int caps_show_cb(struct inode *inode, int mds, void *p)
{
struct ceph_inode_info *ci = ceph_inode(inode);
struct seq_file *s = p;

seq_printf(s, "0x%-17llx%-3d%-17s%-17s\n", ceph_ino(inode),
cap->session->s_mds,
ceph_cap_string(cap->issued),
ceph_cap_string(cap->implemented));
struct ceph_cap *cap;

spin_lock(&ci->i_ceph_lock);
cap = __get_cap_for_mds(ci, mds);
if (cap)
seq_printf(s, "0x%-17llx%-3d%-17s%-17s\n", ceph_ino(inode),
cap->session->s_mds,
ceph_cap_string(cap->issued),
ceph_cap_string(cap->implemented));
spin_unlock(&ci->i_ceph_lock);
return 0;
}

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72 changes: 46 additions & 26 deletions fs/ceph/mds_client.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1632,8 +1632,8 @@ static void cleanup_session_requests(struct ceph_mds_client *mdsc,
* Caller must hold session s_mutex.
*/
int ceph_iterate_session_caps(struct ceph_mds_session *session,
int (*cb)(struct inode *, struct ceph_cap *,
void *), void *arg)
int (*cb)(struct inode *, int mds, void *),
void *arg)
{
struct list_head *p;
struct ceph_cap *cap;
Expand All @@ -1645,13 +1645,16 @@ int ceph_iterate_session_caps(struct ceph_mds_session *session,
spin_lock(&session->s_cap_lock);
p = session->s_caps.next;
while (p != &session->s_caps) {
int mds;

cap = list_entry(p, struct ceph_cap, session_caps);
inode = igrab(&cap->ci->netfs.inode);
if (!inode) {
p = p->next;
continue;
}
session->s_cap_iterator = cap;
mds = cap->mds;
spin_unlock(&session->s_cap_lock);

if (last_inode) {
Expand All @@ -1663,7 +1666,7 @@ int ceph_iterate_session_caps(struct ceph_mds_session *session,
old_cap = NULL;
}

ret = cb(inode, cap, arg);
ret = cb(inode, mds, arg);
last_inode = inode;

spin_lock(&session->s_cap_lock);
Expand Down Expand Up @@ -1696,20 +1699,25 @@ int ceph_iterate_session_caps(struct ceph_mds_session *session,
return ret;
}

static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,
void *arg)
static int remove_session_caps_cb(struct inode *inode, int mds, void *arg)
{
struct ceph_inode_info *ci = ceph_inode(inode);
bool invalidate = false;
int iputs;
struct ceph_cap *cap;
int iputs = 0;

dout("removing cap %p, ci is %p, inode is %p\n",
cap, ci, &ci->netfs.inode);
spin_lock(&ci->i_ceph_lock);
iputs = ceph_purge_inode_cap(inode, cap, &invalidate);
cap = __get_cap_for_mds(ci, mds);
if (cap) {
dout(" removing cap %p, ci is %p, inode is %p\n",
cap, ci, &ci->netfs.inode);

iputs = ceph_purge_inode_cap(inode, cap, &invalidate);
}
spin_unlock(&ci->i_ceph_lock);

wake_up_all(&ci->i_cap_wq);
if (cap)
wake_up_all(&ci->i_cap_wq);
if (invalidate)
ceph_queue_invalidate(inode);
while (iputs--)
Expand Down Expand Up @@ -1780,8 +1788,7 @@ enum {
*
* caller must hold s_mutex.
*/
static int wake_up_session_cb(struct inode *inode, struct ceph_cap *cap,
void *arg)
static int wake_up_session_cb(struct inode *inode, int mds, void *arg)
{
struct ceph_inode_info *ci = ceph_inode(inode);
unsigned long ev = (unsigned long)arg;
Expand All @@ -1792,12 +1799,14 @@ static int wake_up_session_cb(struct inode *inode, struct ceph_cap *cap,
ci->i_requested_max_size = 0;
spin_unlock(&ci->i_ceph_lock);
} else if (ev == RENEWCAPS) {
if (cap->cap_gen < atomic_read(&cap->session->s_cap_gen)) {
/* mds did not re-issue stale cap */
spin_lock(&ci->i_ceph_lock);
struct ceph_cap *cap;

spin_lock(&ci->i_ceph_lock);
cap = __get_cap_for_mds(ci, mds);
/* mds did not re-issue stale cap */
if (cap && cap->cap_gen < atomic_read(&cap->session->s_cap_gen))
cap->issued = cap->implemented = CEPH_CAP_PIN;
spin_unlock(&ci->i_ceph_lock);
}
spin_unlock(&ci->i_ceph_lock);
} else if (ev == FORCE_RO) {
}
wake_up_all(&ci->i_cap_wq);
Expand Down Expand Up @@ -1959,16 +1968,22 @@ static bool drop_negative_children(struct dentry *dentry)
* Yes, this is a bit sloppy. Our only real goal here is to respond to
* memory pressure from the MDS, though, so it needn't be perfect.
*/
static int trim_caps_cb(struct inode *inode, struct ceph_cap *cap, void *arg)
static int trim_caps_cb(struct inode *inode, int mds, void *arg)
{
int *remaining = arg;
struct ceph_inode_info *ci = ceph_inode(inode);
int used, wanted, oissued, mine;
struct ceph_cap *cap;

if (*remaining <= 0)
return -1;

spin_lock(&ci->i_ceph_lock);
cap = __get_cap_for_mds(ci, mds);
if (!cap) {
spin_unlock(&ci->i_ceph_lock);
return 0;
}
mine = cap->issued | cap->implemented;
used = __ceph_caps_used(ci);
wanted = __ceph_caps_file_wanted(ci);
Expand Down Expand Up @@ -3911,26 +3926,22 @@ static struct dentry* d_find_primary(struct inode *inode)
/*
* Encode information about a cap for a reconnect with the MDS.
*/
static int reconnect_caps_cb(struct inode *inode, struct ceph_cap *cap,
void *arg)
static int reconnect_caps_cb(struct inode *inode, int mds, void *arg)
{
union {
struct ceph_mds_cap_reconnect v2;
struct ceph_mds_cap_reconnect_v1 v1;
} rec;
struct ceph_inode_info *ci = cap->ci;
struct ceph_inode_info *ci = ceph_inode(inode);
struct ceph_reconnect_state *recon_state = arg;
struct ceph_pagelist *pagelist = recon_state->pagelist;
struct dentry *dentry;
struct ceph_cap *cap;
char *path;
int pathlen = 0, err;
int pathlen = 0, err = 0;
u64 pathbase;
u64 snap_follows;

dout(" adding %p ino %llx.%llx cap %p %lld %s\n",
inode, ceph_vinop(inode), cap, cap->cap_id,
ceph_cap_string(cap->issued));

dentry = d_find_primary(inode);
if (dentry) {
/* set pathbase to parent dir when msg_version >= 2 */
Expand All @@ -3947,6 +3958,15 @@ static int reconnect_caps_cb(struct inode *inode, struct ceph_cap *cap,
}

spin_lock(&ci->i_ceph_lock);
cap = __get_cap_for_mds(ci, mds);
if (!cap) {
spin_unlock(&ci->i_ceph_lock);
goto out_err;
}
dout(" adding %p ino %llx.%llx cap %p %lld %s\n",
inode, ceph_vinop(inode), cap, cap->cap_id,
ceph_cap_string(cap->issued));

cap->seq = 0; /* reset cap seq */
cap->issue_seq = 0; /* and issue_seq */
cap->mseq = 0; /* and migrate_seq */
Expand Down
3 changes: 1 addition & 2 deletions fs/ceph/mds_client.h
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Original file line number Diff line number Diff line change
Expand Up @@ -541,8 +541,7 @@ extern void ceph_flush_cap_releases(struct ceph_mds_client *mdsc,
extern void ceph_queue_cap_reclaim_work(struct ceph_mds_client *mdsc);
extern void ceph_reclaim_caps_nr(struct ceph_mds_client *mdsc, int nr);
extern int ceph_iterate_session_caps(struct ceph_mds_session *session,
int (*cb)(struct inode *,
struct ceph_cap *, void *),
int (*cb)(struct inode *, int mds, void *),
void *arg);
extern void ceph_mdsc_pre_umount(struct ceph_mds_client *mdsc);

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2 changes: 2 additions & 0 deletions fs/ceph/super.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1192,6 +1192,8 @@ extern void ceph_kick_flushing_caps(struct ceph_mds_client *mdsc,
struct ceph_mds_session *session);
void ceph_kick_flushing_inode_caps(struct ceph_mds_session *session,
struct ceph_inode_info *ci);
extern struct ceph_cap *__get_cap_for_mds(struct ceph_inode_info *ci,
int mds);
extern struct ceph_cap *ceph_get_cap_for_mds(struct ceph_inode_info *ci,
int mds);
extern void ceph_take_cap_refs(struct ceph_inode_info *ci, int caps,
Expand Down

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