2fd752ed77
commit a06247c6804f1a7c86a2e5398a4c1f1db1471848 upstream.
With write operation on psi files replacing old trigger with a new one,
the lifetime of its waitqueue is totally arbitrary. Overwriting an
existing trigger causes its waitqueue to be freed and pending poll()
will stumble on trigger->event_wait which was destroyed.
Fix this by disallowing to redefine an existing psi trigger. If a write
operation is used on a file descriptor with an already existing psi
trigger, the operation will fail with EBUSY error.
Also bypass a check for psi_disabled in the psi_trigger_destroy as the
flag can be flipped after the trigger is created, leading to a memory
leak.
Fixes: 0e94682b73 ("psi: introduce psi monitor")
Reported-by: syzbot+cdb5dd11c97cc532efad@syzkaller.appspotmail.com
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Analyzed-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220111232309.1786347-1-surenb@google.com
[surenb: backported to 5.4 kernel]
CC: stable@vger.kernel.org # 5.4
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
64 lines
1.5 KiB
C
64 lines
1.5 KiB
C
#ifndef _LINUX_PSI_H
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#define _LINUX_PSI_H
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#include <linux/jump_label.h>
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#include <linux/psi_types.h>
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#include <linux/sched.h>
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#include <linux/poll.h>
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struct seq_file;
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struct css_set;
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#ifdef CONFIG_PSI
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extern struct static_key_false psi_disabled;
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extern struct psi_group psi_system;
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void psi_init(void);
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void psi_task_change(struct task_struct *task, int clear, int set);
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void psi_memstall_tick(struct task_struct *task, int cpu);
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void psi_memstall_enter(unsigned long *flags);
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void psi_memstall_leave(unsigned long *flags);
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int psi_show(struct seq_file *s, struct psi_group *group, enum psi_res res);
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#ifdef CONFIG_CGROUPS
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int psi_cgroup_alloc(struct cgroup *cgrp);
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void psi_cgroup_free(struct cgroup *cgrp);
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void cgroup_move_task(struct task_struct *p, struct css_set *to);
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struct psi_trigger *psi_trigger_create(struct psi_group *group,
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char *buf, size_t nbytes, enum psi_res res);
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void psi_trigger_destroy(struct psi_trigger *t);
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__poll_t psi_trigger_poll(void **trigger_ptr, struct file *file,
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poll_table *wait);
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#endif
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#else /* CONFIG_PSI */
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static inline void psi_init(void) {}
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static inline void psi_memstall_enter(unsigned long *flags) {}
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static inline void psi_memstall_leave(unsigned long *flags) {}
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#ifdef CONFIG_CGROUPS
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static inline int psi_cgroup_alloc(struct cgroup *cgrp)
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{
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return 0;
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}
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static inline void psi_cgroup_free(struct cgroup *cgrp)
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{
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}
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static inline void cgroup_move_task(struct task_struct *p, struct css_set *to)
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{
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rcu_assign_pointer(p->cgroups, to);
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}
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#endif
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#endif /* CONFIG_PSI */
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#endif /* _LINUX_PSI_H */
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