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author | Eric W. Biederman <ebiederm@xmission.com> | 2022-02-09 16:22:20 -0600 |
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committer | Eric W. Biederman <ebiederm@xmission.com> | 2022-02-17 09:11:02 -0600 |
commit | a55d07294f1e9b576093bdfa95422f8119941e83 (patch) | |
tree | c570ddac28cfb2800c105baafe568394ce184ceb /kernel | |
parent | 8f2f9c4d82f24f172ae439e5035fc1e0e4c229dd (diff) | |
download | linux-stable-a55d07294f1e9b576093bdfa95422f8119941e83.tar.gz linux-stable-a55d07294f1e9b576093bdfa95422f8119941e83.tar.bz2 linux-stable-a55d07294f1e9b576093bdfa95422f8119941e83.zip |
ucounts: Base set_cred_ucounts changes on the real user
Michal Koutný <mkoutny@suse.com> wrote:
> Tasks are associated to multiple users at once. Historically and as per
> setrlimit(2) RLIMIT_NPROC is enforce based on real user ID.
>
> The commit 21d1c5e386bc ("Reimplement RLIMIT_NPROC on top of ucounts")
> made the accounting structure "indexed" by euid and hence potentially
> account tasks differently.
>
> The effective user ID may be different e.g. for setuid programs but
> those are exec'd into already existing task (i.e. below limit), so
> different accounting is moot.
>
> Some special setresuid(2) users may notice the difference, justifying
> this fix.
I looked at cred->ucount and it is only used for rlimit operations
that were previously stored in cred->user. Making the fact
cred->ucount can refer to a different user from cred->user a bug,
affecting all uses of cred->ulimit not just RLIMIT_NPROC.
Fix set_cred_ucounts to always use the real uid not the effective uid.
Further simplify set_cred_ucounts by noticing that set_cred_ucounts
somehow retained a draft version of the check to see if alloc_ucounts
was needed that checks the new->user and new->user_ns against the
current_real_cred(). Remove that draft version of the check.
All that matters for setting the cred->ucounts are the user_ns and uid
fields in the cred.
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20220207121800.5079-4-mkoutny@suse.com
Link: https://lkml.kernel.org/r/20220216155832.680775-3-ebiederm@xmission.com
Reported-by: Michal Koutný <mkoutny@suse.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Fixes: 21d1c5e386bc ("Reimplement RLIMIT_NPROC on top of ucounts")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/cred.c | 9 |
1 files changed, 2 insertions, 7 deletions
diff --git a/kernel/cred.c b/kernel/cred.c index 473d17c431f3..933155c96922 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -665,21 +665,16 @@ EXPORT_SYMBOL(cred_fscmp); int set_cred_ucounts(struct cred *new) { - struct task_struct *task = current; - const struct cred *old = task->real_cred; struct ucounts *new_ucounts, *old_ucounts = new->ucounts; - if (new->user == old->user && new->user_ns == old->user_ns) - return 0; - /* * This optimization is needed because alloc_ucounts() uses locks * for table lookups. */ - if (old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->euid)) + if (old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->uid)) return 0; - if (!(new_ucounts = alloc_ucounts(new->user_ns, new->euid))) + if (!(new_ucounts = alloc_ucounts(new->user_ns, new->uid))) return -EAGAIN; new->ucounts = new_ucounts; |