4.19-stable review patch. If anyone has any objections, please let me know.
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From: Jens Axboe axboe@kernel.dk
commit f8fa5d76925991976b3e7076f9d1052515ec1fca upstream.
There are multiple ways to grab references to credentials, and the only protection we have against overflowing it is the memory required to do so.
With memory sizes only moving in one direction, let's bump the reference count to 64-bit and move it outside the realm of feasibly overflowing.
Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/cred.h | 6 ++-- kernel/cred.c | 66 +++++++++++++++++++++++++-------------------------- 2 files changed, 36 insertions(+), 36 deletions(-)
--- a/include/linux/cred.h +++ b/include/linux/cred.h @@ -114,7 +114,7 @@ static inline int groups_search(const st * same context as task->real_cred. */ struct cred { - atomic_t usage; + atomic_long_t usage; #ifdef CONFIG_DEBUG_CREDENTIALS atomic_t subscribers; /* number of processes subscribed */ void *put_addr; @@ -231,7 +231,7 @@ static inline bool cap_ambient_invariant */ static inline struct cred *get_new_cred(struct cred *cred) { - atomic_inc(&cred->usage); + atomic_long_inc(&cred->usage); return cred; }
@@ -275,7 +275,7 @@ static inline void put_cred(const struct
if (cred) { validate_creds(cred); - if (atomic_dec_and_test(&(cred)->usage)) + if (atomic_long_dec_and_test(&(cred)->usage)) __put_cred(cred); } } --- a/kernel/cred.c +++ b/kernel/cred.c @@ -101,17 +101,17 @@ static void put_cred_rcu(struct rcu_head
#ifdef CONFIG_DEBUG_CREDENTIALS if (cred->magic != CRED_MAGIC_DEAD || - atomic_read(&cred->usage) != 0 || + atomic_long_read(&cred->usage) != 0 || read_cred_subscribers(cred) != 0) panic("CRED: put_cred_rcu() sees %p with" - " mag %x, put %p, usage %d, subscr %d\n", + " mag %x, put %p, usage %ld, subscr %d\n", cred, cred->magic, cred->put_addr, - atomic_read(&cred->usage), + atomic_long_read(&cred->usage), read_cred_subscribers(cred)); #else - if (atomic_read(&cred->usage) != 0) - panic("CRED: put_cred_rcu() sees %p with usage %d\n", - cred, atomic_read(&cred->usage)); + if (atomic_long_read(&cred->usage) != 0) + panic("CRED: put_cred_rcu() sees %p with usage %ld\n", + cred, atomic_long_read(&cred->usage)); #endif
security_cred_free(cred); @@ -134,11 +134,11 @@ static void put_cred_rcu(struct rcu_head */ void __put_cred(struct cred *cred) { - kdebug("__put_cred(%p{%d,%d})", cred, - atomic_read(&cred->usage), + kdebug("__put_cred(%p{%ld,%d})", cred, + atomic_long_read(&cred->usage), read_cred_subscribers(cred));
- BUG_ON(atomic_read(&cred->usage) != 0); + BUG_ON(atomic_long_read(&cred->usage) != 0); #ifdef CONFIG_DEBUG_CREDENTIALS BUG_ON(read_cred_subscribers(cred) != 0); cred->magic = CRED_MAGIC_DEAD; @@ -161,8 +161,8 @@ void exit_creds(struct task_struct *tsk) { struct cred *cred;
- kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred, - atomic_read(&tsk->cred->usage), + kdebug("exit_creds(%u,%p,%p,{%ld,%d})", tsk->pid, tsk->real_cred, tsk->cred, + atomic_long_read(&tsk->cred->usage), read_cred_subscribers(tsk->cred));
cred = (struct cred *) tsk->real_cred; @@ -197,7 +197,7 @@ const struct cred *get_task_cred(struct do { cred = __task_cred((task)); BUG_ON(!cred); - } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage)); + } while (!atomic_long_inc_not_zero(&((struct cred *)cred)->usage));
rcu_read_unlock(); return cred; @@ -215,7 +215,7 @@ struct cred *cred_alloc_blank(void) if (!new) return NULL;
- atomic_set(&new->usage, 1); + atomic_long_set(&new->usage, 1); #ifdef CONFIG_DEBUG_CREDENTIALS new->magic = CRED_MAGIC; #endif @@ -262,7 +262,7 @@ struct cred *prepare_creds(void) memcpy(new, old, sizeof(struct cred));
new->non_rcu = 0; - atomic_set(&new->usage, 1); + atomic_long_set(&new->usage, 1); set_cred_subscribers(new, 0); get_group_info(new->group_info); get_uid(new->user); @@ -338,8 +338,8 @@ int copy_creds(struct task_struct *p, un p->real_cred = get_cred(p->cred); get_cred(p->cred); alter_cred_subscribers(p->cred, 2); - kdebug("share_creds(%p{%d,%d})", - p->cred, atomic_read(&p->cred->usage), + kdebug("share_creds(%p{%ld,%d})", + p->cred, atomic_long_read(&p->cred->usage), read_cred_subscribers(p->cred)); atomic_inc(&p->cred->user->processes); return 0; @@ -429,8 +429,8 @@ int commit_creds(struct cred *new) struct task_struct *task = current; const struct cred *old = task->real_cred;
- kdebug("commit_creds(%p{%d,%d})", new, - atomic_read(&new->usage), + kdebug("commit_creds(%p{%ld,%d})", new, + atomic_long_read(&new->usage), read_cred_subscribers(new));
BUG_ON(task->cred != old); @@ -439,7 +439,7 @@ int commit_creds(struct cred *new) validate_creds(old); validate_creds(new); #endif - BUG_ON(atomic_read(&new->usage) < 1); + BUG_ON(atomic_long_read(&new->usage) < 1);
get_cred(new); /* we will require a ref for the subj creds too */
@@ -512,14 +512,14 @@ EXPORT_SYMBOL(commit_creds); */ void abort_creds(struct cred *new) { - kdebug("abort_creds(%p{%d,%d})", new, - atomic_read(&new->usage), + kdebug("abort_creds(%p{%ld,%d})", new, + atomic_long_read(&new->usage), read_cred_subscribers(new));
#ifdef CONFIG_DEBUG_CREDENTIALS BUG_ON(read_cred_subscribers(new) != 0); #endif - BUG_ON(atomic_read(&new->usage) < 1); + BUG_ON(atomic_long_read(&new->usage) < 1); put_cred(new); } EXPORT_SYMBOL(abort_creds); @@ -535,8 +535,8 @@ const struct cred *override_creds(const { const struct cred *old = current->cred;
- kdebug("override_creds(%p{%d,%d})", new, - atomic_read(&new->usage), + kdebug("override_creds(%p{%ld,%d})", new, + atomic_long_read(&new->usage), read_cred_subscribers(new));
validate_creds(old); @@ -558,8 +558,8 @@ const struct cred *override_creds(const rcu_assign_pointer(current->cred, new); alter_cred_subscribers(old, -1);
- kdebug("override_creds() = %p{%d,%d}", old, - atomic_read(&old->usage), + kdebug("override_creds() = %p{%ld,%d}", old, + atomic_long_read(&old->usage), read_cred_subscribers(old)); return old; } @@ -576,8 +576,8 @@ void revert_creds(const struct cred *old { const struct cred *override = current->cred;
- kdebug("revert_creds(%p{%d,%d})", old, - atomic_read(&old->usage), + kdebug("revert_creds(%p{%ld,%d})", old, + atomic_long_read(&old->usage), read_cred_subscribers(old));
validate_creds(old); @@ -637,7 +637,7 @@ struct cred *prepare_kernel_cred(struct
*new = *old; new->non_rcu = 0; - atomic_set(&new->usage, 1); + atomic_long_set(&new->usage, 1); set_cred_subscribers(new, 0); get_uid(new->user); get_user_ns(new->user_ns); @@ -760,8 +760,8 @@ static void dump_invalid_creds(const str cred == tsk->cred ? "[eff]" : ""); printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n", cred->magic, cred->put_addr); - printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n", - atomic_read(&cred->usage), + printk(KERN_ERR "CRED: ->usage=%ld, subscr=%d\n", + atomic_long_read(&cred->usage), read_cred_subscribers(cred)); printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n", from_kuid_munged(&init_user_ns, cred->uid), @@ -833,9 +833,9 @@ EXPORT_SYMBOL(__validate_process_creds); */ void validate_creds_for_do_exit(struct task_struct *tsk) { - kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})", + kdebug("validate_creds_for_do_exit(%p,%p{%ld,%d})", tsk->real_cred, tsk->cred, - atomic_read(&tsk->cred->usage), + atomic_long_read(&tsk->cred->usage), read_cred_subscribers(tsk->cred));
__validate_process_creds(tsk, __FILE__, __LINE__);