From: Shuning Zhang Date: Mon, 15 Apr 2019 15:01:37 +0000 (+0800) Subject: cifs: Fix use after free of a mid_q_entry X-Git-Tag: v4.1.12-124.31.3~167 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=268dafb7aa1740ebb11ae3d43a9bb8a9de0347ac;p=users%2Fjedix%2Flinux-maple.git cifs: Fix use after free of a mid_q_entry With protocol version 2.0 mounts we have seen crashes with corrupt mid entries. Either the server->pending_mid_q list becomes corrupt with a cyclic reference in one element or a mid object fetched by the demultiplexer thread becomes overwritten during use. Code review identified a race between the demultiplexer thread and the request issuing thread. The demultiplexer thread seems to be written with the assumption that it is the sole user of the mid object until it calls the mid callback which either wakes the issuer task or deletes the mid. This assumption is not true because the issuer task can be woken up earlier by a signal. If the demultiplexer thread has proceeded as far as setting the mid_state to MID_RESPONSE_RECEIVED then the issuer thread will happily end up calling cifs_delete_mid while the demultiplexer thread still is using the mid object. Inserting a delay in the cifs demultiplexer thread widens the race window and makes reproduction of the race very easy: if (server->large_buf) buf = server->bigbuf; + usleep_range(500, 4000); server->lstrp = jiffies; To resolve this I think the proper solution involves putting a reference count on the mid object. This patch makes sure that the demultiplexer thread holds a reference until it has finished processing the transaction. Cc: stable@vger.kernel.org Signed-off-by: Lars Persson Acked-by: Paulo Alcantara Reviewed-by: Ronnie Sahlberg Reviewed-by: Pavel Shilovsky Signed-off-by: Steve French (cherry picked from commit 696e420bb2a6624478105651d5368d45b502b324) Orabug: 29654888 Signed-off-by: Shuning Zhang Reviewed-by: Darren Kenny Signed-off-by: Brian Maly Conflicts: fs/cifs/connect.c fs/cifs/smb2ops.c fs/cifs/smb2transport.c fs/cifs/transport.c [ connect.c: contextual has changed. smb2ops.c: hdr->Command changed to shdr->Command in the third line. ^ smb2transport.c: contextual has changed, the codes are the a statement block of else, but this statement block has been moved outside. transport.c: contextual has changed, the codes are the a statement block of else, but this statement block has been moved outside. ] Signed-off-by: Brian Maly --- diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h index 22b289a3b1c4..443ab7df5df1 100644 --- a/fs/cifs/cifsglob.h +++ b/fs/cifs/cifsglob.h @@ -1254,6 +1254,7 @@ typedef void (mid_callback_t)(struct mid_q_entry *mid); /* one of these for every pending CIFS request to the server */ struct mid_q_entry { struct list_head qhead; /* mids waiting on reply from this server */ + struct kref refcount; struct TCP_Server_Info *server; /* server corresponding to this mid */ __u64 mid; /* multiplex id */ __u32 pid; /* process id */ diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h index c63fd1dde25b..14a8c8db497b 100644 --- a/fs/cifs/cifsproto.h +++ b/fs/cifs/cifsproto.h @@ -73,6 +73,7 @@ extern struct mid_q_entry *AllocMidQEntry(const struct smb_hdr *smb_buffer, struct TCP_Server_Info *server); extern void DeleteMidQEntry(struct mid_q_entry *midEntry); extern void cifs_delete_mid(struct mid_q_entry *mid); +extern void cifs_mid_q_entry_release(struct mid_q_entry *midEntry); extern void cifs_wake_up_task(struct mid_q_entry *mid); extern int cifs_call_async(struct TCP_Server_Info *server, struct smb_rqst *rqst, diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index 4fcd6f1b3484..64eaa3c25927 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -900,8 +900,11 @@ cifs_demultiplex_thread(void *p) else length = mid_entry->receive(server, mid_entry); - if (length < 0) + if (length < 0) { + if (mid_entry) + cifs_mid_q_entry_release(mid_entry); continue; + } if (server->large_buf) buf = server->bigbuf; @@ -910,6 +913,8 @@ cifs_demultiplex_thread(void *p) if (mid_entry != NULL) { if (!mid_entry->multiRsp || mid_entry->multiEnd) mid_entry->callback(mid_entry); + + cifs_mid_q_entry_release(mid_entry); } else if (!server->ops->is_oplock_break || !server->ops->is_oplock_break(buf, server)) { cifs_dbg(VFS, "No task to wake, unknown frame received! NumMids %d\n", diff --git a/fs/cifs/smb1ops.c b/fs/cifs/smb1ops.c index fc537c29044e..d5f8c9703ebf 100644 --- a/fs/cifs/smb1ops.c +++ b/fs/cifs/smb1ops.c @@ -105,6 +105,7 @@ cifs_find_mid(struct TCP_Server_Info *server, char *buffer) if (compare_mid(mid->mid, buf) && mid->mid_state == MID_REQUEST_SUBMITTED && le16_to_cpu(mid->command) == buf->Command) { + kref_get(&mid->refcount); spin_unlock(&GlobalMid_Lock); return mid; } diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c index 57aeae6116d6..35cd9185f1ad 100644 --- a/fs/cifs/smb2ops.c +++ b/fs/cifs/smb2ops.c @@ -187,6 +187,7 @@ smb2_find_mid(struct TCP_Server_Info *server, char *buf) if ((mid->mid == wire_mid) && (mid->mid_state == MID_REQUEST_SUBMITTED) && (mid->command == hdr->Command)) { + kref_get(&mid->refcount); spin_unlock(&GlobalMid_Lock); return mid; } diff --git a/fs/cifs/smb2transport.c b/fs/cifs/smb2transport.c index d4c5b6f109a7..6e5e8643037c 100644 --- a/fs/cifs/smb2transport.c +++ b/fs/cifs/smb2transport.c @@ -490,6 +490,7 @@ smb2_mid_entry_alloc(const struct smb2_hdr *smb_buffer, return temp; else { memset(temp, 0, sizeof(struct mid_q_entry)); + kref_init(&temp->refcount); temp->mid = le64_to_cpu(smb_buffer->MessageId); temp->pid = current->pid; temp->command = smb_buffer->Command; /* Always LE */ diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c index 66106f6ed7b4..25a192161ddb 100644 --- a/fs/cifs/transport.c +++ b/fs/cifs/transport.c @@ -58,6 +58,7 @@ AllocMidQEntry(const struct smb_hdr *smb_buffer, struct TCP_Server_Info *server) return temp; else { memset(temp, 0, sizeof(struct mid_q_entry)); + kref_init(&temp->refcount); temp->mid = get_mid(smb_buffer); temp->pid = current->pid; temp->command = cpu_to_le16(smb_buffer->Command); @@ -80,6 +81,21 @@ AllocMidQEntry(const struct smb_hdr *smb_buffer, struct TCP_Server_Info *server) return temp; } +static void _cifs_mid_q_entry_release(struct kref *refcount) +{ + struct mid_q_entry *mid = container_of(refcount, struct mid_q_entry, + refcount); + + mempool_free(mid, cifs_mid_poolp); +} + +void cifs_mid_q_entry_release(struct mid_q_entry *midEntry) +{ + spin_lock(&GlobalMid_Lock); + kref_put(&midEntry->refcount, _cifs_mid_q_entry_release); + spin_unlock(&GlobalMid_Lock); +} + void DeleteMidQEntry(struct mid_q_entry *midEntry) { @@ -108,7 +124,7 @@ DeleteMidQEntry(struct mid_q_entry *midEntry) } } #endif - mempool_free(midEntry, cifs_mid_poolp); + cifs_mid_q_entry_release(midEntry); } void