@@ -610,15 +610,6 @@ nfsd4_create(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
switch (create->cr_type) {
case NF4LNK:
- /* ugh! we have to null-terminate the linktext, or
- * vfs_symlink() will choke. it is always safe to
- * null-terminate by brute force, since at worst we
- * will overwrite the first byte of the create namelen
- * in the XDR buffer, which has already been extracted
- * during XDR decode.
- */
- create->cr_linkname[create->cr_linklen] = 0;
-
status = nfsd_symlink(rqstp, &cstate->current_fh,
create->cr_name, create->cr_namelen,
create->cr_linkname, create->cr_linklen,
@@ -594,7 +594,18 @@ nfsd4_decode_create(struct nfsd4_compoundargs *argp, struct nfsd4_create *create
READ_BUF(4);
READ32(create->cr_linklen);
READ_BUF(create->cr_linklen);
- SAVEMEM(create->cr_linkname, create->cr_linklen);
+ /*
+ * The VFS will want a null-terminated string, and
+ * null-terminating in place isn't safe since this might
+ * end on a page boundary:
+ */
+ create->cr_linkname =
+ kmalloc(create->cr_linklen + 1, GFP_KERNEL);
+ if (!create->cr_linkname)
+ return nfserr_jukebox;
+ memcpy(create->cr_linkname, p, create->cr_linklen);
+ create->cr_linkname[create->cr_linklen] = '\0';
+ defer_free(argp, kfree, create->cr_linkname);
break;
case NF4BLK:
case NF4CHR:
This is a note to let you know that I have just added a patch titled nfsd: fix rare symlink decoding bug to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.11.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From 47ae6f2b596a64e823d4d0e73f5b67831d051779 Mon Sep 17 00:00:00 2001 From: "J. Bruce Fields" <bfields@redhat.com> Date: Thu, 19 Jun 2014 16:44:48 -0400 Subject: nfsd: fix rare symlink decoding bug commit 76f47128f9b33af1e96819746550d789054c9664 upstream. An NFS operation that creates a new symlink includes the symlink data, which is xdr-encoded as a length followed by the data plus 0 to 3 bytes of zero-padding as required to reach a 4-byte boundary. The vfs, on the other hand, wants null-terminated data. The simple way to handle this would be by copying the data into a newly allocated buffer with space for the final null. The current nfsd_symlink code tries to be more clever by skipping that step in the (likely) case where the byte following the string is already 0. But that assumes that the byte following the string is ours to look at. In fact, it might be the first byte of a page that we can't read, or of some object that another task might modify. Worse, the NFSv4 code tries to fix the problem by actually writing to that byte. In the NFSv2/v3 cases this actually appears to be safe: - nfs3svc_decode_symlinkargs explicitly null-terminates the data (after first checking its length and copying it to a new page). - NFSv2 limits symlinks to 1k. The buffer holding the rpc request is always at least a page, and the link data (and previous fields) have maximum lengths that prevent the request from reaching the end of a page. In the NFSv4 case the CREATE op is potentially just one part of a long compound so can end up on the end of a page if you're unlucky. The minimal fix here is to copy and null-terminate in the NFSv4 case. The nfsd_symlink() interface here seems too fragile, though. It should really either do the copy itself every time or just require a null-terminated string. Reported-by: Jeff Layton <jlayton@primarydata.com> Signed-off-by: J. Bruce Fields <bfields@redhat.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- fs/nfsd/nfs4proc.c | 9 --------- fs/nfsd/nfs4xdr.c | 13 ++++++++++++- 2 files changed, 12 insertions(+), 10 deletions(-) -- 1.9.1