From: Dan Carpenter Date: Tue, 5 May 2020 18:33:31 +0000 (+0300) Subject: ovl: potential crash in ovl_fid_to_fh() X-Git-Tag: v5.15~3633^2~27 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=9aafc1b0187322fa4fd4eb905d0903172237206c;p=platform%2Fkernel%2Flinux-starfive.git 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 Reviewed-by: Amir Goldstein Cc: # v5.5 Signed-off-by: Miklos Szeredi --- diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c index 475c61f..ed5c107 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);