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authorLinus Torvalds <torvalds@linux-foundation.org>2022-02-20 10:44:11 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2022-02-20 10:44:11 -0800
commit2d3409ebc87f4bc4ed23bd39e78db9ffc29eec44 (patch)
tree9d8b0917fec278f9b01cbf1e637752a7dbdc7d61
parent4f12b742eb2b3a850ac8be7dc4ed52976fc6cb0b (diff)
parent0cbae9e24fa7d6c6e9f828562f084da82217a0c5 (diff)
downloadlwn-2d3409ebc87f4bc4ed23bd39e78db9ffc29eec44.tar.gz
lwn-2d3409ebc87f4bc4ed23bd39e78db9ffc29eec44.zip
Merge branch 'ucount-rlimit-fixes-for-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull ucounts fixes from Eric Biederman: "Michal Koutný recently found some bugs in the enforcement of RLIMIT_NPROC in the recent ucount rlimit implementation. In this set of patches I have developed a very conservative approach changing only what is necessary to fix the bugs that I can see clearly. Cleanups and anything that is making the code more consistent can follow after we have the code working as it has historically. The problem is not so much inconsistencies (although those exist) but that it is very difficult to figure out what the code should be doing in the case of RLIMIT_NPROC. All other rlimits are only enforced where the resource is acquired (allocated). RLIMIT_NPROC by necessity needs to be enforced in an additional location, and our current implementation stumbled it's way into that implementation" * 'ucount-rlimit-fixes-for-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: ucounts: Handle wrapping in is_ucounts_overlimit ucounts: Move RLIMIT_NPROC handling after set_user ucounts: Base set_cred_ucounts changes on the real user ucounts: Enforce RLIMIT_NPROC not RLIMIT_NPROC+1 rlimit: Fix RLIMIT_NPROC enforcement failure caused by capability calls in set_user
-rw-r--r--kernel/cred.c9
-rw-r--r--kernel/fork.c10
-rw-r--r--kernel/sys.c20
-rw-r--r--kernel/ucount.c3
4 files changed, 23 insertions, 19 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;
diff --git a/kernel/fork.c b/kernel/fork.c
index d75a528f7b21..17d8a8c85e3b 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2021,18 +2021,18 @@ static __latent_entropy struct task_struct *copy_process(
#ifdef CONFIG_PROVE_LOCKING
DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
#endif
+ retval = copy_creds(p, clone_flags);
+ if (retval < 0)
+ goto bad_fork_free;
+
retval = -EAGAIN;
if (is_ucounts_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
if (p->real_cred->user != INIT_USER &&
!capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
- goto bad_fork_free;
+ goto bad_fork_cleanup_count;
}
current->flags &= ~PF_NPROC_EXCEEDED;
- retval = copy_creds(p, clone_flags);
- if (retval < 0)
- goto bad_fork_free;
-
/*
* If multiple threads are within copy_process(), then this check
* triggers too late. This doesn't hurt, the check is only there
diff --git a/kernel/sys.c b/kernel/sys.c
index ecc4cf019242..97dc9e5d6bf9 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -472,6 +472,16 @@ static int set_user(struct cred *new)
if (!new_user)
return -EAGAIN;
+ free_uid(new->user);
+ new->user = new_user;
+ return 0;
+}
+
+static void flag_nproc_exceeded(struct cred *new)
+{
+ if (new->ucounts == current_ucounts())
+ return;
+
/*
* We don't fail in case of NPROC limit excess here because too many
* poorly written programs don't check set*uid() return code, assuming
@@ -480,15 +490,10 @@ static int set_user(struct cred *new)
* failure to the execve() stage.
*/
if (is_ucounts_overlimit(new->ucounts, UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC)) &&
- new_user != INIT_USER &&
- !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
+ new->user != INIT_USER)
current->flags |= PF_NPROC_EXCEEDED;
else
current->flags &= ~PF_NPROC_EXCEEDED;
-
- free_uid(new->user);
- new->user = new_user;
- return 0;
}
/*
@@ -563,6 +568,7 @@ long __sys_setreuid(uid_t ruid, uid_t euid)
if (retval < 0)
goto error;
+ flag_nproc_exceeded(new);
return commit_creds(new);
error:
@@ -625,6 +631,7 @@ long __sys_setuid(uid_t uid)
if (retval < 0)
goto error;
+ flag_nproc_exceeded(new);
return commit_creds(new);
error:
@@ -704,6 +711,7 @@ long __sys_setresuid(uid_t ruid, uid_t euid, uid_t suid)
if (retval < 0)
goto error;
+ flag_nproc_exceeded(new);
return commit_creds(new);
error:
diff --git a/kernel/ucount.c b/kernel/ucount.c
index 65b597431c86..06ea04d44685 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -350,7 +350,8 @@ bool is_ucounts_overlimit(struct ucounts *ucounts, enum ucount_type type, unsign
if (rlimit > LONG_MAX)
max = LONG_MAX;
for (iter = ucounts; iter; iter = iter->ns->ucounts) {
- if (get_ucounts_value(iter, type) > max)
+ long val = get_ucounts_value(iter, type);
+ if (val < 0 || val > max)
return true;
max = READ_ONCE(iter->ns->ucount_max[type]);
}