From: Dan Carpenter dan.carpenter@oracle.com
[ Upstream commit 9aafc1b0187322fa4fd4eb905d0903172237206c ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- fs/overlayfs/export.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c index 6f54d70cef27..e605017031ee 100644 --- a/fs/overlayfs/export.c +++ b/fs/overlayfs/export.c @@ -777,6 +777,9 @@ 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);