From 01332b03706686a8df32ed76ac564f679c3ad2e2 Mon Sep 17 00:00:00 2001 From: Pavel Shilovsky Date: Wed, 23 Oct 2019 15:37:19 -0700 Subject: [PATCH] CIFS: Fix use after free of file info structures commit 1a67c415965752879e2e9fad407bc44fc7f25f23 upstream. Currently the code assumes that if a file info entry belongs to lists of open file handles of an inode and a tcon then it has non-zero reference. The recent changes broke that assumption when putting the last reference of the file info. There may be a situation when a file is being deleted but nothing prevents another thread to reference it again and start using it. This happens because we do not hold the inode list lock while checking the number of references of the file info structure. Fix this by doing the proper locking when doing the check. Fixes: 487317c99477d ("cifs: add spinlock for the openFileList to cifsInodeInfo") Fixes: cb248819d209d ("cifs: use cifsInodeInfo->open_file_lock while iterating to avoid a panic") Cc: Stable Reviewed-by: Ronnie Sahlberg Signed-off-by: Pavel Shilovsky Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman --- fs/cifs/file.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/cifs/file.c b/fs/cifs/file.c index 617f86b..b4e33ef 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -403,10 +403,11 @@ void _cifsFileInfo_put(struct cifsFileInfo *cifs_file, bool wait_oplock_handler) bool oplock_break_cancelled; spin_lock(&tcon->open_file_lock); - + spin_lock(&cifsi->open_file_lock); spin_lock(&cifs_file->file_info_lock); if (--cifs_file->count > 0) { spin_unlock(&cifs_file->file_info_lock); + spin_unlock(&cifsi->open_file_lock); spin_unlock(&tcon->open_file_lock); return; } @@ -419,9 +420,7 @@ void _cifsFileInfo_put(struct cifsFileInfo *cifs_file, bool wait_oplock_handler) cifs_add_pending_open_locked(&fid, cifs_file->tlink, &open); /* remove it from the lists */ - spin_lock(&cifsi->open_file_lock); list_del(&cifs_file->flist); - spin_unlock(&cifsi->open_file_lock); list_del(&cifs_file->tlist); if (list_empty(&cifsi->openFileList)) { @@ -437,6 +436,7 @@ void _cifsFileInfo_put(struct cifsFileInfo *cifs_file, bool wait_oplock_handler) cifs_set_oplock_level(cifsi, 0); } + spin_unlock(&cifsi->open_file_lock); spin_unlock(&tcon->open_file_lock); oplock_break_cancelled = wait_oplock_handler ? -- 2.7.4