2020-08-05 19:27:41

by Jeffrey Mitchell

Subject: [PATCH] nfs: Fix getxattr kernel panic and memory overflow

Move the buffer size check to decode_attr_security_label() before memcpy()
Only call memcpy() if the buffer is large enough

Signed-off-by: Jeffrey Mitchell <[email protected]>
---
fs/nfs/nfs4proc.c | 2 --
fs/nfs/nfs4xdr.c | 5 ++++-
2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 2e2dac29a9e9..45e0585e0667 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -5845,8 +5845,6 @@ static int _nfs4_get_security_label(struct inode *inode, void *buf,
return ret;
if (!(fattr.valid & NFS_ATTR_FATTR_V4_SECURITY_LABEL))
return -ENOENT;
- if (buflen < label.len)
- return -ERANGE;
return 0;
}

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 47817ef0aadb..50162e0a959c 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -4166,7 +4166,10 @@ static int decode_attr_security_label(struct xdr_stream *xdr, uint32_t *bitmap,
return -EIO;
if (len < NFS4_MAXLABELLEN) {
if (label) {
- memcpy(label->label, p, len);
+ if (label->len && label->len < len)
+ return -ERANGE;
+ if (label->len)
+ memcpy(label->label, p, len);
label->len = len;
label->pi = pi;
label->lfs = lfs;
--
2.25.1

2020-08-11 14:09:53

by Trond Myklebust

Subject: Re: [PATCH] nfs: Fix getxattr kernel panic and memory overflow

On Wed, 2020-08-05 at 12:23 -0500, Jeffrey Mitchell wrote:
> Move the buffer size check to decode_attr_security_label() before
> memcpy()
> Only call memcpy() if the buffer is large enough
>
> Signed-off-by: Jeffrey Mitchell <[email protected]>
> ---
> fs/nfs/nfs4proc.c | 2 --
> fs/nfs/nfs4xdr.c | 5 ++++-
> 2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index 2e2dac29a9e9..45e0585e0667 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -5845,8 +5845,6 @@ static int _nfs4_get_security_label(struct
> inode *inode, void *buf,
> return ret;
> if (!(fattr.valid & NFS_ATTR_FATTR_V4_SECURITY_LABEL))
> return -ENOENT;
> - if (buflen < label.len)
> - return -ERANGE;
> return 0;
> }
>
> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
> index 47817ef0aadb..50162e0a959c 100644
> --- a/fs/nfs/nfs4xdr.c
> +++ b/fs/nfs/nfs4xdr.c
> @@ -4166,7 +4166,10 @@ static int decode_attr_security_label(struct
> xdr_stream *xdr, uint32_t *bitmap,
> return -EIO;
> if (len < NFS4_MAXLABELLEN) {
> if (label) {
> - memcpy(label->label, p, len);
> + if (label->len && label->len < len)
> + return -ERANGE;
> + if (label->len)
> + memcpy(label->label, p, len);

Just a heads up that I fixed this to avoid the duplicate test of label-
>len != 0 and I added a Fixes: before applying.

> label->len = len;
> label->pi = pi;
> label->lfs = lfs;
--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
[email protected]