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apparmor: ensure WB_HISTORY_SIZE value is a power of 2

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[ Upstream commit 6c055e62560b958354625604293652753d82bcae ]

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: 136db99485 ("apparmor: increase left match history buffer size")

Signed-off-by: Ryan Lee <ryan.lee@canonical.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Ryan Lee
2025-05-01 12:54:38 -07:00
committed by Greg Kroah-Hartman
parent 77d2993d8b
commit eda378a0ab
2 changed files with 3 additions and 1 deletions
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3
security/apparmor/include/match.h
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@@ -141,7 +141,8 @@ unsigned int aa_dfa_matchn_until(struct aa_dfa *dfa, unsigned int 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;

1
security/apparmor/match.c
View File

@@ -672,6 +672,7 @@ unsigned int aa_dfa_matchn_until(struct aa_dfa *dfa, unsigned int 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)