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9p locks: fix glock.client_id leak in do_lock 

the 9p client code overwrites our glock.client_id pointing to a static
buffer by an allocated string holding the network provided value which
we do not care about; free and reset the value as appropriate.

This is almost identical to the leak in v9fs_file_getlock() fixed by
Al Viro in commit ce85dd58ad ("9p: we are leaking glock.client_id
in v9fs_file_getlock()"), which was returned as an error by a coverity
false positive -- while we are here attempt to make the code slightly
more robust to future change of the net/9p/client code and hopefully
more clear to coverity that there is no problem.

Link: http://lkml.kernel.org/r/1536339057-21974-5-git-send-email-asmadeus@codewreck.org
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
This commit is contained in:
Dominique Martinet 2018-09-08 01:18:43 +09:00
parent ef5305f1f7
commit b4dc44b3ca
1 changed files with 14 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
fs/9p/vfs_file.c
View File

@ -208,6 +208,14 @@ static int v9fs_file_do_lock(struct file *filp, int cmd, struct file_lock *fl)
if (schedule_timeout_interruptible(v9ses->session_lock_timeout)
!= 0)
break;
/*
* p9_client_lock_dotl overwrites flock.client_id with the
* server message, free and reuse the client name
*/
if (flock.client_id != fid->clnt->name) {
kfree(flock.client_id);
flock.client_id = fid->clnt->name;
}
}
/* map 9p status to VFS status */
@ -239,6 +247,8 @@ out_unlock:
locks_lock_file_wait(filp, fl);
fl->fl_type = fl_type;
}
if (flock.client_id != fid->clnt->name)
kfree(flock.client_id);
out:
return res;
}
@ -273,7 +283,7 @@ static int v9fs_file_getlock(struct file *filp, struct file_lock *fl)
res = p9_client_getlock_dotl(fid, &glock);
if (res < 0)
return res;
goto out;
/* map 9p lock type to os lock type */
switch (glock.type) {
case P9_LOCK_TYPE_RDLCK:
@ -294,7 +304,9 @@ static int v9fs_file_getlock(struct file *filp, struct file_lock *fl)
fl->fl_end = glock.start + glock.length - 1;
fl->fl_pid = -glock.proc_id;
}
kfree(glock.client_id);
out:
if (glock.client_id != fid->clnt->name)
kfree(glock.client_id);
return res;
}