Re: [PATCH] cifs: setcifsacl - Send the actual (security descriptor) buffer size instead of the pre-allocated size

[Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>]

On Sat, 2017-08-26 at 22:23 -0500, shirishpargaonkar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:
> From: Shirish Pargaonkar <shirishpargaonkar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> 
> 
> Instead of sending allocated buffer size of a security descriptor,
> send the actual size of the security descriptor during set cifs acl
> operation.
> 
> 
> Signed-off-by: Shirish Pargaonkar <shirishpargaonkar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Tested-by: Paul van Schayck <polleke-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> ---
>  setcifsacl.c | 58 +++++++++++++++++++++++++++++++++++++---------------------
>  1 file changed, 37 insertions(+), 21 deletions(-)
> 
> diff --git a/setcifsacl.c b/setcifsacl.c
> index 7eeeaa6..0d4b15f 100644
> --- a/setcifsacl.c
> +++ b/setcifsacl.c
> @@ -50,24 +50,33 @@ enum setcifsacl_actions {
>  static void *plugin_handle;
>  static bool plugin_loaded;
>  
> -static void
> +static int
>  copy_cifs_sid(struct cifs_sid *dst, const struct cifs_sid *src)
>  {
> -	int i;
> +	int i, size = 0;
>  
>  	dst->revision = src->revision;
> +	size += sizeof(uint8_t);
> +
>  	dst->num_subauth = src->num_subauth;
> +	size += sizeof(uint8_t);
> +
>  	for (i = 0; i < NUM_AUTHS; i++)
>  		dst->authority[i] = src->authority[i];
> +	size += (sizeof(uint8_t) * NUM_AUTHS);
> +
>  	for (i = 0; i < src->num_subauth; i++)
>  		dst->sub_auth[i] = src->sub_auth[i];
> +	size += (sizeof(uint32_t) * src->num_subauth);
> +
> +	return size;
>  }
>  
>  static void
>  copy_sec_desc(const struct cifs_ntsd *pntsd, struct cifs_ntsd *pnntsd,
> -		int numaces, int acessize)
> +		int numaces, int acessize, ssize_t *bufsize)

A return pointer in a void return function is a little inefficient. How
about making this function return ssize_t instead?

>  {
> -	int osidsoffset, gsidsoffset, dacloffset;
> +	int size, osidsoffset, gsidsoffset, dacloffset;
>  	struct cifs_sid *owner_sid_ptr, *group_sid_ptr;
>  	struct cifs_sid *nowner_sid_ptr, *ngroup_sid_ptr;
>  	struct cifs_ctrl_acl *dacl_ptr, *ndacl_ptr;
> @@ -77,28 +86,34 @@ copy_sec_desc(const struct cifs_ntsd *pntsd, struct cifs_ntsd *pnntsd,
>  	gsidsoffset = le32toh(pntsd->gsidoffset);
>  	dacloffset = le32toh(pntsd->dacloffset);
>  
> +	size = sizeof(struct cifs_ntsd);
>  	pnntsd->revision = pntsd->revision;
>  	pnntsd->type = pntsd->type;
>  	pnntsd->osidoffset = pntsd->osidoffset;
>  	pnntsd->gsidoffset = pntsd->gsidoffset;
>  	pnntsd->dacloffset = pntsd->dacloffset;
> +	*bufsize = *bufsize + size;

Here you're assuming that the size being passed in is always 0. Is that
a safe assumption? Would it be better to have it just do this there?

    *bufsize = size;

>  
>  	dacl_ptr = (struct cifs_ctrl_acl *)((char *)pntsd + dacloffset);
>  	ndacl_ptr = (struct cifs_ctrl_acl *)((char *)pnntsd + dacloffset);
>  
> +	size = acessize + sizeof(struct cifs_ctrl_acl);
>  	ndacl_ptr->revision = dacl_ptr->revision;
> -	ndacl_ptr->size = htole16(acessize + sizeof(struct cifs_ctrl_acl));
> +	ndacl_ptr->size = htole16(size);
>  	ndacl_ptr->num_aces = htole32(numaces);
> +	*bufsize = *bufsize + size;
>  
>  	/* copy owner sid */
>  	owner_sid_ptr = (struct cifs_sid *)((char *)pntsd + osidsoffset);
>  	nowner_sid_ptr = (struct cifs_sid *)((char *)pnntsd + osidsoffset);
> -	copy_cifs_sid(nowner_sid_ptr, owner_sid_ptr);
> +	size = copy_cifs_sid(nowner_sid_ptr, owner_sid_ptr);
> +	*bufsize = *bufsize + size;
>  
>  	/* copy group sid */
>  	group_sid_ptr = (struct cifs_sid *)((char *)pntsd + gsidsoffset);
>  	ngroup_sid_ptr = (struct cifs_sid *)((char *)pnntsd + gsidsoffset);
> -	copy_cifs_sid(ngroup_sid_ptr, group_sid_ptr);
> +	size = copy_cifs_sid(ngroup_sid_ptr, group_sid_ptr);
> +	*bufsize = *bufsize + size;
>  
>  	return;
>  }
> @@ -156,10 +171,10 @@ compare_aces(struct cifs_ace *sace, struct cifs_ace *dace, int compflags)
>  }
>  
>  static int
> -get_sec_desc_size(struct cifs_ntsd *pntsd, struct cifs_ntsd **npntsd,
> -			int aces, ssize_t *bufsize, size_t *acesoffset)
> +alloc_sec_desc(struct cifs_ntsd *pntsd, struct cifs_ntsd **npntsd,
> +			int aces, size_t *acesoffset)
>  {
> -	unsigned int size, acessize, dacloffset;
> +	unsigned int size, acessize, bufsize, dacloffset;
>  
>  	size = sizeof(struct cifs_ntsd) +
>  		2 * sizeof(struct cifs_sid) +
> @@ -169,9 +184,9 @@ get_sec_desc_size(struct cifs_ntsd *pntsd, struct cifs_ntsd **npntsd,
>  
>  	*acesoffset = dacloffset + sizeof(struct cifs_ctrl_acl);
>  	acessize = aces * sizeof(struct cifs_ace);
> -	*bufsize = size + acessize;
> +	bufsize = size + acessize;
>  
> -	*npntsd = malloc(*bufsize);
> +	*npntsd = malloc(bufsize);
>  	if (!*npntsd) {
>  		printf("%s: Memory allocation failure", __func__);
>  		return errno;
> @@ -188,7 +203,7 @@ ace_set(struct cifs_ntsd *pntsd, struct cifs_ntsd **npntsd, ssize_t *bufsize,
>  	size_t acesoffset;
>  	char *acesptr;
>  
> -	rc = get_sec_desc_size(pntsd, npntsd, numcaces, bufsize, &acesoffset);
> +	rc = alloc_sec_desc(pntsd, npntsd, numcaces, &acesoffset);
>  	if (rc)
>  		return rc;
>  
> @@ -198,9 +213,8 @@ ace_set(struct cifs_ntsd *pntsd, struct cifs_ntsd **npntsd, ssize_t *bufsize,
>  		acessize += size;
>  		acesptr += size;
>  	}
> -	copy_sec_desc(pntsd, *npntsd, numcaces, acessize);
> -	acesptr = (char *)*npntsd + acesoffset;
>  
> +	copy_sec_desc(pntsd, *npntsd, numcaces, acessize, bufsize);
>  
>  	return 0;
>  }
> @@ -215,7 +229,7 @@ ace_add(struct cifs_ntsd *pntsd, struct cifs_ntsd **npntsd, ssize_t *bufsize,
>  	char *acesptr;
>  
>  	numaces = numfaces + numcaces;
> -	rc = get_sec_desc_size(pntsd, npntsd, numaces, bufsize, &acesoffset);
> +	rc = alloc_sec_desc(pntsd, npntsd, numaces, &acesoffset);
>  	if (rc)
>  		return rc;
>  
> @@ -230,7 +244,8 @@ ace_add(struct cifs_ntsd *pntsd, struct cifs_ntsd **npntsd, ssize_t *bufsize,
>  		acesptr += size;
>  		acessize += size;
>  	}
> -	copy_sec_desc(pntsd, *npntsd, numaces, acessize);
> +
> +	copy_sec_desc(pntsd, *npntsd, numaces, acessize, bufsize);
>  
>  	return 0;
>  }
> @@ -249,7 +264,7 @@ ace_modify(struct cifs_ntsd *pntsd, struct cifs_ntsd **npntsd, ssize_t *bufsize,
>  		return -1;
>  	}
>  
> -	rc = get_sec_desc_size(pntsd, npntsd, numfaces, bufsize, &acesoffset);
> +	rc = alloc_sec_desc(pntsd, npntsd, numfaces, &acesoffset);
>  	if (rc)
>  		return rc;
>  
> @@ -270,7 +285,7 @@ ace_modify(struct cifs_ntsd *pntsd, struct cifs_ntsd **npntsd, ssize_t *bufsize,
>  		acessize += size;
>  	}
>  
> -	copy_sec_desc(pntsd, *npntsd, numfaces, acessize);
> +	copy_sec_desc(pntsd, *npntsd, numfaces, acessize, bufsize);
>  
>  	return 0;
>  }
> @@ -294,7 +309,7 @@ ace_delete(struct cifs_ntsd *pntsd, struct cifs_ntsd **npntsd, ssize_t *bufsize,
>  		return -1;
>  	}
>  
> -	rc = get_sec_desc_size(pntsd, npntsd, numfaces, bufsize, &acesoffset);
> +	rc = alloc_sec_desc(pntsd, npntsd, numfaces, &acesoffset);
>  	if (rc)
>  		return rc;
>  
> @@ -317,7 +332,8 @@ ace_delete(struct cifs_ntsd *pntsd, struct cifs_ntsd **npntsd, ssize_t *bufsize,
>  		printf("%s: Nothing to delete\n", __func__);
>  		return 1;
>  	}
> -	copy_sec_desc(pntsd, *npntsd, numaces, acessize);
> +
> +	copy_sec_desc(pntsd, *npntsd, numaces, acessize, bufsize);
>  
>  	return 0;
>  }

Thanks for the patch. I'll plan to look more in detail tomorrow. Could
you explain a little about this bug was manifested? Is there a public
bug tracker link of some sort?

(PS for Steve: we don't really have a stable branch for cifs-utils.
Distros are on their own there.)
-- 
Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>