Commit 6c055e62 authored by Ryan Lee's avatar Ryan Lee Committed by John Johansen
Browse files

apparmor: ensure WB_HISTORY_SIZE value is a power of 2 



WB_HISTORY_SIZE was defined to be a value not a power of 2, despite a
comment in the declaration of struct match_workbuf stating it is and a
modular arithmetic usage in the inc_wb_pos macro assuming that it is. Bump
WB_HISTORY_SIZE's value up to 32 and add a BUILD_BUG_ON_NOT_POWER_OF_2
line to ensure that any future changes to the value of WB_HISTORY_SIZE
respect this requirement.

Fixes: 136db994 ("apparmor: increase left match history buffer size")

Signed-off-by: default avatarRyan Lee <ryan.lee@canonical.com>
Signed-off-by: default avatarJohn Johansen <john.johansen@canonical.com>
parent a949b46e

security/apparmor/include/match.h

+2 −1
Original line number Diff line number Diff line
@@ -137,7 +137,8 @@ aa_state_t aa_dfa_matchn_until(struct aa_dfa *dfa, aa_state_t start, 


void aa_dfa_free_kref(struct kref *kref);



#define WB_HISTORY_SIZE 24

/* This needs to be a power of 2 */

#define WB_HISTORY_SIZE 32

struct match_workbuf {

	unsigned int count;

	unsigned int pos;

security/apparmor/match.c

+1 −0
Original line number Diff line number Diff line
@@ -681,6 +681,7 @@ aa_state_t aa_dfa_matchn_until(struct aa_dfa *dfa, aa_state_t start, 


#define inc_wb_pos(wb)						\

do {								\

	BUILD_BUG_ON_NOT_POWER_OF_2(WB_HISTORY_SIZE);			\

	wb->pos = (wb->pos + 1) & (WB_HISTORY_SIZE - 1);		\

	wb->len = (wb->len + 1) & (WB_HISTORY_SIZE - 1);		\

} while (0)