Re: [PATCH] apparmor: Constify 'nulldfa_src' and 'stacksplitdfa_src' arrays

Re: [PATCH] apparmor: Constify 'nulldfa_src' and 'stacksplitdfa_src' arrays

[Len Bao]

Hi,

On Sun, May 24, 2026 at 11:34:11AM +0000, Len Bao wrote:
> The 'nulldfa_src' and 'stacksplitdfa_src' arrays are initialized in
> their declarations and never changed. So, constify them to reduce the
> attack surface.
> 
> To make this possible, it is also necessary to change the 'unpack_table'
> and 'aa_dfa_unpack' function prototypes to pass, as a first argument, a
> pointer to a 'const' blob. At the same type, define the blob exact
> pointer type (pointer to const char) since all the calls to the
> mentioned functions use this same type.
> 
> Before the patch (size lsm.o):
> 
>   text	   data	    bss	    dec	    hex
> 128768	  28028	    704	 157500	  2673c
> 
> After the patch (size lsm.o):
> 
>   text	   data	    bss	    dec	    hex
> 131264	  25532	    704	 157500	  2673c
> 
> Signed-off-by: Len Bao <len.bao@gmx.us>
> ---

Friendly ping.
Any comments are welcome.

Regards,
Len

>  security/apparmor/include/match.h | 2 +-
>  security/apparmor/lsm.c           | 4 ++--
>  security/apparmor/match.c         | 6 +++---
>  3 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/security/apparmor/include/match.h b/security/apparmor/include/match.h
> index 7accb1c39..4a92cd044 100644
> --- a/security/apparmor/include/match.h
> +++ b/security/apparmor/include/match.h
> @@ -125,7 +125,7 @@ static inline size_t table_size(size_t len, size_t el_size)
>  
>  #define aa_state_t unsigned int
>  
> -struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags);
> +struct aa_dfa *aa_dfa_unpack(const char *blob, size_t size, int flags);
>  aa_state_t aa_dfa_match_len(struct aa_dfa *dfa, aa_state_t start,
>  			    const char *str, int len);
>  aa_state_t aa_dfa_match(struct aa_dfa *dfa, aa_state_t start,
> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
> index 3491e9f60..3f995b6a7 100644
> --- a/security/apparmor/lsm.c
> +++ b/security/apparmor/lsm.c
> @@ -2432,12 +2432,12 @@ static int __init apparmor_nf_ip_init(void)
>  }
>  #endif
>  
> -static char nulldfa_src[] __aligned(8) = {
> +static const char nulldfa_src[] __aligned(8) = {
>  	#include "nulldfa.in"
>  };
>  static struct aa_dfa *nulldfa;
>  
> -static char stacksplitdfa_src[] __aligned(8) = {
> +static const char stacksplitdfa_src[] __aligned(8) = {
>  	#include "stacksplitdfa.in"
>  };
>  struct aa_dfa *stacksplitdfa;
> diff --git a/security/apparmor/match.c b/security/apparmor/match.c
> index 3a2c6cf02..c6f7bea1e 100644
> --- a/security/apparmor/match.c
> +++ b/security/apparmor/match.c
> @@ -31,7 +31,7 @@
>   *
>   * NOTE: must be freed by kvfree (not kfree)
>   */
> -static struct table_header *unpack_table(char *blob, size_t bsize)
> +static struct table_header *unpack_table(const char *blob, size_t bsize)
>  {
>  	struct table_header *table = NULL;
>  	struct table_header th;
> @@ -311,11 +311,11 @@ static struct table_header *remap_data16_to_data32(struct table_header *old)
>   *
>   * Returns: an unpacked dfa ready for matching or ERR_PTR on failure
>   */
> -struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags)
> +struct aa_dfa *aa_dfa_unpack(const char *blob, size_t size, int flags)
>  {
>  	int hsize;
>  	int error = -ENOMEM;
> -	char *data = blob;
> +	const char *data = blob;
>  	struct table_header *table = NULL;
>  	struct aa_dfa *dfa = kzalloc_obj(struct aa_dfa);
>  	if (!dfa)
> -- 
> 2.43.0
>