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| author | Dan Carpenter <dan.carpenter@oracle.com> | 2020-05-05 21:33:31 +0300 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2020-05-13 11:10:57 +0200 |
| commit | 9aafc1b0187322fa4fd4eb905d0903172237206c (patch) | |
| tree | f3c897f0dd4775ab542d1398ed12f147c0935fa3 /fs/overlayfs | |
| parent | 15fd2ea9f4f3d85fef787ba7db1b87939d0a2754 (diff) | |
| download | lwn-9aafc1b0187322fa4fd4eb905d0903172237206c.tar.gz lwn-9aafc1b0187322fa4fd4eb905d0903172237206c.zip | |
ovl: potential crash in ovl_fid_to_fh()
The "buflen" value comes from the user and there is a potential that it
could be zero. In do_handle_to_path() we know that "handle->handle_bytes"
is non-zero and we do:
handle_dwords = handle->handle_bytes >> 2;
So values 1-3 become zero. Then in ovl_fh_to_dentry() we do:
int len = fh_len << 2;
So now len is in the "0,4-128" range and a multiple of 4. But if
"buflen" is zero it will try to copy negative bytes when we do the
memcpy in ovl_fid_to_fh().
memcpy(&fh->fb, fid, buflen - OVL_FH_WIRE_OFFSET);
And that will lead to a crash. Thanks to Amir Goldstein for his help
with this patch.
Fixes: cbe7fba8edfc ("ovl: make sure that real fid is 32bit aligned in memory")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Cc: <stable@vger.kernel.org> # v5.5
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/overlayfs')
| -rw-r--r-- | fs/overlayfs/export.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c index 475c61f53f0f..ed5c1078919c 100644 --- a/fs/overlayfs/export.c +++ b/fs/overlayfs/export.c @@ -783,6 +783,9 @@ static struct ovl_fh *ovl_fid_to_fh(struct fid *fid, int buflen, int fh_type) if (fh_type != OVL_FILEID_V0) return ERR_PTR(-EINVAL); + if (buflen <= OVL_FH_WIRE_OFFSET) + return ERR_PTR(-EINVAL); + fh = kzalloc(buflen, GFP_KERNEL); if (!fh) return ERR_PTR(-ENOMEM); |