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authorWill Deacon <will.deacon@arm.com>2013-08-21 21:24:47 +0400
committerEric Van Hensbergen <ericvh@gmail.com>2013-08-26 19:28:46 +0400
commit50192abe02929586111fb33f216060a9341875f1 (patch)
treec766629c78fc8410eb452e018b0ba4b629141a3e
parente0d6cb9cd3a3ac8a3b8e5b22b83c4f8619786f22 (diff)
downloadlinux-50192abe02929586111fb33f216060a9341875f1.tar.xz
fs/9p: avoid accessing utsname after namespace has been torn down
During trinity fuzzing in a kvmtool guest, I stumbled across the following: Unable to handle kernel NULL pointer dereference at virtual address 00000004 PC is at v9fs_file_do_lock+0xc8/0x1a0 LR is at v9fs_file_do_lock+0x48/0x1a0 [<c01e2ed0>] (v9fs_file_do_lock+0xc8/0x1a0) from [<c0119154>] (locks_remove_flock+0x8c/0x124) [<c0119154>] (locks_remove_flock+0x8c/0x124) from [<c00d9bf0>] (__fput+0x58/0x1e4) [<c00d9bf0>] (__fput+0x58/0x1e4) from [<c0044340>] (task_work_run+0xac/0xe8) [<c0044340>] (task_work_run+0xac/0xe8) from [<c002e36c>] (do_exit+0x6bc/0x8d8) [<c002e36c>] (do_exit+0x6bc/0x8d8) from [<c002e674>] (do_group_exit+0x3c/0xb0) [<c002e674>] (do_group_exit+0x3c/0xb0) from [<c002e6f8>] (__wake_up_parent+0x0/0x18) I believe this is due to an attempt to access utsname()->nodename, after exit_task_namespaces() has been called, leaving current->nsproxy->uts_ns as NULL and causing the above dereference. A similar issue was fixed for lockd in 9a1b6bf818e7 ("LOCKD: Don't call utsname()->nodename from nlmclnt_setlockargs"), so this patch attempts something similar for 9pfs. Cc: Eric Van Hensbergen <ericvh@gmail.com> Cc: Ron Minnich <rminnich@sandia.gov> Cc: Latchesar Ionkov <lucho@ionkov.net> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
-rw-r--r--fs/9p/vfs_file.c4
-rw-r--r--include/net/9p/client.h5
-rw-r--r--net/9p/client.c5
3 files changed, 12 insertions, 2 deletions
diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index d384a8b77ee8..aa5ecf479a57 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -183,7 +183,7 @@ static int v9fs_file_do_lock(struct file *filp, int cmd, struct file_lock *fl)
else
flock.length = fl->fl_end - fl->fl_start + 1;
flock.proc_id = fl->fl_pid;
- flock.client_id = utsname()->nodename;
+ flock.client_id = fid->clnt->name;
if (IS_SETLKW(cmd))
flock.flags = P9_LOCK_FLAGS_BLOCK;
@@ -260,7 +260,7 @@ static int v9fs_file_getlock(struct file *filp, struct file_lock *fl)
else
glock.length = fl->fl_end - fl->fl_start + 1;
glock.proc_id = fl->fl_pid;
- glock.client_id = utsname()->nodename;
+ glock.client_id = fid->clnt->name;
res = p9_client_getlock_dotl(fid, &glock);
if (res < 0)
diff --git a/include/net/9p/client.h b/include/net/9p/client.h
index 4c7c01a73911..c38a005bd0cf 100644
--- a/include/net/9p/client.h
+++ b/include/net/9p/client.h
@@ -26,6 +26,8 @@
#ifndef NET_9P_CLIENT_H
#define NET_9P_CLIENT_H
+#include <linux/utsname.h>
+
/* Number of requests per row */
#define P9_ROW_MAXTAG 255
@@ -134,6 +136,7 @@ struct p9_req_t {
* @tagpool - transaction id accounting for session
* @reqs - 2D array of requests
* @max_tag - current maximum tag id allocated
+ * @name - node name used as client id
*
* The client structure is used to keep track of various per-client
* state that has been instantiated.
@@ -164,6 +167,8 @@ struct p9_client {
struct p9_idpool *tagpool;
struct p9_req_t *reqs[P9_ROW_MAXTAG];
int max_tag;
+
+ char name[__NEW_UTS_LEN + 1];
};
/**
diff --git a/net/9p/client.c b/net/9p/client.c
index 8b93cae2d11d..0e49b288e574 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -992,6 +992,7 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
{
int err;
struct p9_client *clnt;
+ char *client_id;
err = 0;
clnt = kmalloc(sizeof(struct p9_client), GFP_KERNEL);
@@ -1000,6 +1001,10 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
clnt->trans_mod = NULL;
clnt->trans = NULL;
+
+ client_id = utsname()->nodename;
+ memcpy(clnt->name, client_id, strlen(client_id) + 1);
+
spin_lock_init(&clnt->lock);
INIT_LIST_HEAD(&clnt->fidlist);