The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3cb6ee991496b67ee284c6895a0ba007e2d7bac3 Mon Sep 17 00:00:00 2001 From: Christian Brauner christian.brauner@ubuntu.com Date: Mon, 29 Nov 2021 12:44:34 +0100 Subject: [PATCH] 9p: only copy valid iattrs in 9P2000.L setattr implementation

The 9P2000.L setattr method v9fs_vfs_setattr_dotl() copies struct iattr values without checking whether they are valid causing unitialized values to be copied. The 9P2000 setattr method v9fs_vfs_setattr() method gets this right. Check whether struct iattr fields are valid first before copying in v9fs_vfs_setattr_dotl() too and make sure that all other fields are set to 0 apart from {g,u}id which should be set to INVALID_{G,U}ID. This ensure that they can be safely sent over the wire or printed for debugging later on.

Link: https://lkml.kernel.org/r/20211129114434.3637938-1-brauner@kernel.org Link: https://lkml.kernel.org/r/000000000000a0d53f05d1c72a4c%40google.com Cc: Eric Van Hensbergen ericvh@gmail.com Cc: Latchesar Ionkov lucho@ionkov.net Cc: Dominique Martinet asmadeus@codewreck.org Cc: stable@kernel.org Cc: v9fs-developer@lists.sourceforge.net Reported-by: syzbot+dfac92a50024b54acaa4@syzkaller.appspotmail.com Signed-off-by: Christian Brauner christian.brauner@ubuntu.com [Dominique: do not set a/mtime with just ATTR_A/MTIME as discussed] Signed-off-by: Dominique Martinet asmadeus@codewreck.org

diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c index 7dee89ba32e7..52f8ae79db21 100644 --- a/fs/9p/vfs_inode_dotl.c +++ b/fs/9p/vfs_inode_dotl.c @@ -551,7 +551,10 @@ int v9fs_vfs_setattr_dotl(struct user_namespace *mnt_userns, { int retval, use_dentry = 0; struct p9_fid *fid = NULL; - struct p9_iattr_dotl p9attr; + struct p9_iattr_dotl p9attr = { + .uid = INVALID_UID, + .gid = INVALID_GID, + }; struct inode *inode = d_inode(dentry);

p9_debug(P9_DEBUG_VFS, "\n"); @@ -561,14 +564,22 @@ int v9fs_vfs_setattr_dotl(struct user_namespace *mnt_userns, return retval;

p9attr.valid = v9fs_mapped_iattr_valid(iattr->ia_valid); - p9attr.mode = iattr->ia_mode; - p9attr.uid = iattr->ia_uid; - p9attr.gid = iattr->ia_gid; - p9attr.size = iattr->ia_size; - p9attr.atime_sec = iattr->ia_atime.tv_sec; - p9attr.atime_nsec = iattr->ia_atime.tv_nsec; - p9attr.mtime_sec = iattr->ia_mtime.tv_sec; - p9attr.mtime_nsec = iattr->ia_mtime.tv_nsec; + if (iattr->ia_valid & ATTR_MODE) + p9attr.mode = iattr->ia_mode; + if (iattr->ia_valid & ATTR_UID) + p9attr.uid = iattr->ia_uid; + if (iattr->ia_valid & ATTR_GID) + p9attr.gid = iattr->ia_gid; + if (iattr->ia_valid & ATTR_SIZE) + p9attr.size = iattr->ia_size; + if (iattr->ia_valid & ATTR_ATIME_SET) { + p9attr.atime_sec = iattr->ia_atime.tv_sec; + p9attr.atime_nsec = iattr->ia_atime.tv_nsec; + } + if (iattr->ia_valid & ATTR_MTIME_SET) { + p9attr.mtime_sec = iattr->ia_mtime.tv_sec; + p9attr.mtime_nsec = iattr->ia_mtime.tv_nsec; + }

if (iattr->ia_valid & ATTR_FILE) { fid = iattr->ia_file->private_data;