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authorDavid Disseldorp <ddiss@suse.de>2015-03-13 14:20:29 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-04-19 10:10:50 +0200
commit57cf01ac9ff841958cbed2b727c271ab420b0ffa (patch)
treee90109ef8d4ab6c86c614de05f920eb129adcdcc /fs
parent2cb264a36f293b3a50809324abea2aff4889af60 (diff)
downloadlinux-linaro-stable-57cf01ac9ff841958cbed2b727c271ab420b0ffa.tar.gz
cifs: fix use-after-free bug in find_writable_file
commit e1e9bda22d7ddf88515e8fe401887e313922823e upstream. Under intermittent network outages, find_writable_file() is susceptible to the following race condition, which results in a user-after-free in the cifs_writepages code-path: Thread 1 Thread 2 ======== ======== inv_file = NULL refind = 0 spin_lock(&cifs_file_list_lock) // invalidHandle found on openFileList inv_file = open_file // inv_file->count currently 1 cifsFileInfo_get(inv_file) // inv_file->count = 2 spin_unlock(&cifs_file_list_lock); cifs_reopen_file() cifs_close() // fails (rc != 0) ->cifsFileInfo_put() spin_lock(&cifs_file_list_lock) // inv_file->count = 1 spin_unlock(&cifs_file_list_lock) spin_lock(&cifs_file_list_lock); list_move_tail(&inv_file->flist, &cifs_inode->openFileList); spin_unlock(&cifs_file_list_lock); cifsFileInfo_put(inv_file); ->spin_lock(&cifs_file_list_lock) // inv_file->count = 0 list_del(&cifs_file->flist); // cleanup!! kfree(cifs_file); spin_unlock(&cifs_file_list_lock); spin_lock(&cifs_file_list_lock); ++refind; // refind = 1 goto refind_writable; At this point we loop back through with an invalid inv_file pointer and a refind value of 1. On second pass, inv_file is not overwritten on openFileList traversal, and is subsequently dereferenced. Signed-off-by: David Disseldorp <ddiss@suse.de> Reviewed-by: Jeff Layton <jlayton@samba.org> Signed-off-by: Steve French <smfrench@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/cifs/file.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 5fcc10fa62bd..f4a8577c3e91 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -1789,6 +1789,7 @@ refind_writable:
cifsFileInfo_put(inv_file);
spin_lock(&cifs_file_list_lock);
++refind;
+ inv_file = NULL;
goto refind_writable;
}
}