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landlock: Use bit-fields for storing handled layer access masks

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When defined using bit-fields, the compiler takes care of packing the
bits in a memory-efficient way and frees us from defining
LANDLOCK_SHIFT_ACCESS_* by hand.  The exact memory layout does not
matter in our use case.

The manual definition of LANDLOCK_SHIFT_ACCESS_* has resulted in bugs in
at least two recent patch sets [1] [2] where new kinds of handled access
rights were introduced.

Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
Cc: Tahera Fahimi <fahimitahera@gmail.com>
Link: https://lore.kernel.org/r/ebd680cc-25d6-ee14-4856-310f5e5e28e4@huawei-partners.com [1]
Link: https://lore.kernel.org/r/ZmLEoBfHyUR3nKAV@google.com [2]
Signed-off-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20240610082115.1693267-1-gnoack@google.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
This commit is contained in:
Günther Noack 2024-06-10 08:21:15 +00:00 committed by Mickaël Salaün
parent 256abd8e55
commit 395a02d04e
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GPG Key ID: E5E3D0E88C82F6D2
3 changed files with 9 additions and 21 deletions
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2
security/landlock/limits.h
View File

@ -21,12 +21,10 @@
#define LANDLOCK_LAST_ACCESS_FS LANDLOCK_ACCESS_FS_IOCTL_DEV
#define LANDLOCK_MASK_ACCESS_FS ((LANDLOCK_LAST_ACCESS_FS << 1) - 1)
#define LANDLOCK_NUM_ACCESS_FS __const_hweight64(LANDLOCK_MASK_ACCESS_FS)
#define LANDLOCK_SHIFT_ACCESS_FS 0
#define LANDLOCK_LAST_ACCESS_NET LANDLOCK_ACCESS_NET_CONNECT_TCP
#define LANDLOCK_MASK_ACCESS_NET ((LANDLOCK_LAST_ACCESS_NET << 1) - 1)
#define LANDLOCK_NUM_ACCESS_NET __const_hweight64(LANDLOCK_MASK_ACCESS_NET)
#define LANDLOCK_SHIFT_ACCESS_NET LANDLOCK_NUM_ACCESS_FS
/* clang-format on */

4
security/landlock/ruleset.c
View File

@ -169,13 +169,9 @@ static void build_check_ruleset(void)
.num_rules = ~0,
.num_layers = ~0,
};
typeof(ruleset.access_masks[0]) access_masks = ~0;
BUILD_BUG_ON(ruleset.num_rules < LANDLOCK_MAX_NUM_RULES);
BUILD_BUG_ON(ruleset.num_layers < LANDLOCK_MAX_NUM_LAYERS);
BUILD_BUG_ON(access_masks <
((LANDLOCK_MASK_ACCESS_FS << LANDLOCK_SHIFT_ACCESS_FS) |
(LANDLOCK_MASK_ACCESS_NET << LANDLOCK_SHIFT_ACCESS_NET)));
}
/**

24
security/landlock/ruleset.h
View File

@ -39,10 +39,10 @@ static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_NET);
static_assert(sizeof(unsigned long) >= sizeof(access_mask_t));
/* Ruleset access masks. */
typedef u32 access_masks_t;
/* Makes sure all ruleset access rights can be stored. */
static_assert(BITS_PER_TYPE(access_masks_t) >=
LANDLOCK_NUM_ACCESS_FS + LANDLOCK_NUM_ACCESS_NET);
struct access_masks {
access_mask_t fs : LANDLOCK_NUM_ACCESS_FS;
access_mask_t net : LANDLOCK_NUM_ACCESS_NET;
};
typedef u16 layer_mask_t;
/* Makes sure all layers can be checked. */
@ -226,7 +226,7 @@ struct landlock_ruleset {
* layers are set once and never changed for the
* lifetime of the ruleset.
*/
access_masks_t access_masks[];
struct access_masks access_masks[];
};
};
};
@ -265,8 +265,7 @@ landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset,
/* Should already be checked in sys_landlock_create_ruleset(). */
WARN_ON_ONCE(fs_access_mask != fs_mask);
ruleset->access_masks[layer_level] |=
(fs_mask << LANDLOCK_SHIFT_ACCESS_FS);
ruleset->access_masks[layer_level].fs |= fs_mask;
}
static inline void
@ -278,17 +277,14 @@ landlock_add_net_access_mask(struct landlock_ruleset *const ruleset,
/* Should already be checked in sys_landlock_create_ruleset(). */
WARN_ON_ONCE(net_access_mask != net_mask);
ruleset->access_masks[layer_level] |=
(net_mask << LANDLOCK_SHIFT_ACCESS_NET);
ruleset->access_masks[layer_level].net |= net_mask;
}
static inline access_mask_t
landlock_get_raw_fs_access_mask(const struct landlock_ruleset *const ruleset,
const u16 layer_level)
{
return (ruleset->access_masks[layer_level] >>
LANDLOCK_SHIFT_ACCESS_FS) &
LANDLOCK_MASK_ACCESS_FS;
return ruleset->access_masks[layer_level].fs;
}
static inline access_mask_t
@ -304,9 +300,7 @@ static inline access_mask_t
landlock_get_net_access_mask(const struct landlock_ruleset *const ruleset,
const u16 layer_level)
{
return (ruleset->access_masks[layer_level] >>
LANDLOCK_SHIFT_ACCESS_NET) &
LANDLOCK_MASK_ACCESS_NET;
return ruleset->access_masks[layer_level].net;
}
bool landlock_unmask_layers(const struct landlock_rule *const rule,