Messages in this thread | | | Date | Wed, 23 Mar 2022 10:38:52 -0700 | Subject | Re: [RFC PATCH v1] LSM: Remove double path_rename hook calls for RENAME_EXCHANGE | From | John Johansen <> |
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Looks good to me. Of course now I am going to have to create a follow-up patch to optimize the apparmor mediation.
Acked-by: John Johansen <john.johansen@canonical.com>
On 3/23/22 01:40, Mickaël Salaün wrote: > Any comment? John, Tetsuo, does it look OK for AppArmor and Tomoyo? > > On 22/02/2022 18:53, Mickaël Salaün wrote: >> From: Mickaël Salaün <mic@linux.microsoft.com> >> >> In order to be able to identify a file exchange with renameat2(2) and >> RENAME_EXCHANGE, which will be useful for Landlock [1], propagate the >> rename flags to LSMs. This may also improve performance because of the >> switch from two set of LSM hook calls to only one, and because LSMs >> using this hook may optimize the double check (e.g. only one lock, >> reduce the number of path walks). >> >> AppArmor, Landlock and Tomoyo are updated to leverage this change. This >> should not change the current behavior (same check order), except >> (different level of) speed boosts. >> >> [1] https://lore.kernel.org/r/20220221212522.320243-1-mic@digikod.net >> >> Cc: James Morris <jmorris@namei.org> >> Cc: John Johansen <john.johansen@canonical.com> >> Cc: Kentaro Takeda <takedakn@nttdata.co.jp> >> Cc: Serge E. Hallyn <serge@hallyn.com> >> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> >> Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> >> Link: https://lore.kernel.org/r/20220222175332.384545-1-mic@digikod.net >> --- >> include/linux/lsm_hook_defs.h | 2 +- >> include/linux/lsm_hooks.h | 1 + >> security/apparmor/lsm.c | 30 +++++++++++++++++++++++++----- >> security/landlock/fs.c | 12 ++++++++++-- >> security/security.c | 9 +-------- >> security/tomoyo/tomoyo.c | 11 ++++++++++- >> 6 files changed, 48 insertions(+), 17 deletions(-) >> >> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h >> index 819ec92dc2a8..d8b49c9c3a8a 100644 >> --- a/include/linux/lsm_hook_defs.h >> +++ b/include/linux/lsm_hook_defs.h >> @@ -100,7 +100,7 @@ LSM_HOOK(int, 0, path_link, struct dentry *old_dentry, >> const struct path *new_dir, struct dentry *new_dentry) >> LSM_HOOK(int, 0, path_rename, const struct path *old_dir, >> struct dentry *old_dentry, const struct path *new_dir, >> - struct dentry *new_dentry) >> + struct dentry *new_dentry, unsigned int flags) >> LSM_HOOK(int, 0, path_chmod, const struct path *path, umode_t mode) >> LSM_HOOK(int, 0, path_chown, const struct path *path, kuid_t uid, kgid_t gid) >> LSM_HOOK(int, 0, path_chroot, const struct path *path) >> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h >> index 3bf5c658bc44..32cd2a7fe9fc 100644 >> --- a/include/linux/lsm_hooks.h >> +++ b/include/linux/lsm_hooks.h >> @@ -358,6 +358,7 @@ >> * @old_dentry contains the dentry structure of the old link. >> * @new_dir contains the path structure for parent of the new link. >> * @new_dentry contains the dentry structure of the new link. >> + * @flags may contain rename options such as RENAME_EXCHANGE. >> * Return 0 if permission is granted. >> * @path_chmod: >> * Check for permission to change a mode of the file @path. The new >> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c >> index 4f0eecb67dde..900bc540656a 100644 >> --- a/security/apparmor/lsm.c >> +++ b/security/apparmor/lsm.c >> @@ -354,13 +354,16 @@ static int apparmor_path_link(struct dentry *old_dentry, const struct path *new_ >> } >> static int apparmor_path_rename(const struct path *old_dir, struct dentry *old_dentry, >> - const struct path *new_dir, struct dentry *new_dentry) >> + const struct path *new_dir, struct dentry *new_dentry, >> + const unsigned int flags) >> { >> struct aa_label *label; >> int error = 0; >> if (!path_mediated_fs(old_dentry)) >> return 0; >> + if ((flags & RENAME_EXCHANGE) && !path_mediated_fs(new_dentry)) >> + return 0; >> label = begin_current_label_crit_section(); >> if (!unconfined(label)) { >> @@ -374,10 +377,27 @@ static int apparmor_path_rename(const struct path *old_dir, struct dentry *old_d >> d_backing_inode(old_dentry)->i_mode >> }; >> - error = aa_path_perm(OP_RENAME_SRC, label, &old_path, 0, >> - MAY_READ | AA_MAY_GETATTR | MAY_WRITE | >> - AA_MAY_SETATTR | AA_MAY_DELETE, >> - &cond); >> + if (flags & RENAME_EXCHANGE) { >> + struct path_cond cond_exchange = { >> + i_uid_into_mnt(mnt_userns, d_backing_inode(new_dentry)), >> + d_backing_inode(new_dentry)->i_mode >> + }; >> + >> + error = aa_path_perm(OP_RENAME_SRC, label, &new_path, 0, >> + MAY_READ | AA_MAY_GETATTR | MAY_WRITE | >> + AA_MAY_SETATTR | AA_MAY_DELETE, >> + &cond_exchange); >> + if (!error) >> + error = aa_path_perm(OP_RENAME_DEST, label, &old_path, >> + 0, MAY_WRITE | AA_MAY_SETATTR | >> + AA_MAY_CREATE, &cond_exchange); >> + } >> + >> + if (!error) >> + error = aa_path_perm(OP_RENAME_SRC, label, &old_path, 0, >> + MAY_READ | AA_MAY_GETATTR | MAY_WRITE | >> + AA_MAY_SETATTR | AA_MAY_DELETE, >> + &cond); >> if (!error) >> error = aa_path_perm(OP_RENAME_DEST, label, &new_path, >> 0, MAY_WRITE | AA_MAY_SETATTR | >> diff --git a/security/landlock/fs.c b/security/landlock/fs.c >> index 97b8e421f617..7e57fca6e814 100644 >> --- a/security/landlock/fs.c >> +++ b/security/landlock/fs.c >> @@ -574,10 +574,12 @@ static inline u32 maybe_remove(const struct dentry *const dentry) >> static int hook_path_rename(const struct path *const old_dir, >> struct dentry *const old_dentry, >> const struct path *const new_dir, >> - struct dentry *const new_dentry) >> + struct dentry *const new_dentry, >> + const unsigned int flags) >> { >> const struct landlock_ruleset *const dom = >> landlock_get_current_domain(); >> + u32 exchange_access = 0; >> if (!dom) >> return 0; >> @@ -585,11 +587,17 @@ static int hook_path_rename(const struct path *const old_dir, >> if (old_dir->dentry != new_dir->dentry) >> /* Gracefully forbids reparenting. */ >> return -EXDEV; >> + if (flags & RENAME_EXCHANGE) { >> + if (unlikely(d_is_negative(new_dentry))) >> + return -ENOENT; >> + exchange_access = >> + get_mode_access(d_backing_inode(new_dentry)->i_mode); >> + } >> if (unlikely(d_is_negative(old_dentry))) >> return -ENOENT; >> /* RENAME_EXCHANGE is handled because directories are the same. */ >> return check_access_path(dom, old_dir, maybe_remove(old_dentry) | >> - maybe_remove(new_dentry) | >> + maybe_remove(new_dentry) | exchange_access | >> get_mode_access(d_backing_inode(old_dentry)->i_mode)); >> } >> diff --git a/security/security.c b/security/security.c >> index 22261d79f333..8634da4cfd46 100644 >> --- a/security/security.c >> +++ b/security/security.c >> @@ -1184,15 +1184,8 @@ int security_path_rename(const struct path *old_dir, struct dentry *old_dentry, >> (d_is_positive(new_dentry) && IS_PRIVATE(d_backing_inode(new_dentry))))) >> return 0; >> - if (flags & RENAME_EXCHANGE) { >> - int err = call_int_hook(path_rename, 0, new_dir, new_dentry, >> - old_dir, old_dentry); >> - if (err) >> - return err; >> - } >> - >> return call_int_hook(path_rename, 0, old_dir, old_dentry, new_dir, >> - new_dentry); >> + new_dentry, flags); >> } >> EXPORT_SYMBOL(security_path_rename); >> diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c >> index b6a31901f289..71e82d855ebf 100644 >> --- a/security/tomoyo/tomoyo.c >> +++ b/security/tomoyo/tomoyo.c >> @@ -264,17 +264,26 @@ static int tomoyo_path_link(struct dentry *old_dentry, const struct path *new_di >> * @old_dentry: Pointer to "struct dentry". >> * @new_parent: Pointer to "struct path". >> * @new_dentry: Pointer to "struct dentry". >> + * @flags: Rename options. >> * >> * Returns 0 on success, negative value otherwise. >> */ >> static int tomoyo_path_rename(const struct path *old_parent, >> struct dentry *old_dentry, >> const struct path *new_parent, >> - struct dentry *new_dentry) >> + struct dentry *new_dentry, >> + const unsigned int flags) >> { >> struct path path1 = { .mnt = old_parent->mnt, .dentry = old_dentry }; >> struct path path2 = { .mnt = new_parent->mnt, .dentry = new_dentry }; >> + if (flags & RENAME_EXCHANGE) { >> + const int err = tomoyo_path2_perm(TOMOYO_TYPE_RENAME, &path2, >> + &path1); >> + >> + if (err) >> + return err; >> + } >> return tomoyo_path2_perm(TOMOYO_TYPE_RENAME, &path1, &path2); >> } >> >> base-commit: cfb92440ee71adcc2105b0890bb01ac3cddb8507
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