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| author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2007-10-01 12:20:13 +0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-10-01 18:52:23 +0400 |
| commit | 9f96cb1e8bca179a92afa40dfc3c49990f1cfc71 (patch) | |
| tree | 7d1f921f488aa570083420dc3846856b17a7b2b6 /kernel/futex_compat.c | |
| parent | 8792f961ba8057d9f27987def3600253a3ba060f (diff) | |
| download | linux-9f96cb1e8bca179a92afa40dfc3c49990f1cfc71.tar.xz | |
robust futex thread exit race
Calling handle_futex_death in exit_robust_list for the different robust
mutexes of a thread basically frees the mutex. Another thread might grab
the lock immediately which updates the next pointer of the mutex.
fetch_robust_entry over the next pointer might therefore branch into the
robust mutex list of a different thread. This can cause two problems: 1)
some mutexes held by the dead thread are not getting freed and 2) some
mutexs held by a different thread are freed.
The next point need to be read before calling handle_futex_death.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/futex_compat.c')
| -rw-r--r-- | kernel/futex_compat.c | 28 |
1 files changed, 18 insertions, 10 deletions
diff --git a/kernel/futex_compat.c b/kernel/futex_compat.c index 7e52eb051f22..2c2e2954b713 100644 --- a/kernel/futex_compat.c +++ b/kernel/futex_compat.c @@ -38,10 +38,11 @@ fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry, void compat_exit_robust_list(struct task_struct *curr) { struct compat_robust_list_head __user *head = curr->compat_robust_list; - struct robust_list __user *entry, *pending; - unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; - compat_uptr_t uentry, upending; + struct robust_list __user *entry, *next_entry, *pending; + unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip; + compat_uptr_t uentry, next_uentry, upending; compat_long_t futex_offset; + int rc; /* * Fetch the list head (which was registered earlier, via @@ -61,11 +62,16 @@ void compat_exit_robust_list(struct task_struct *curr) if (fetch_robust_entry(&upending, &pending, &head->list_op_pending, &pip)) return; - if (pending) - handle_futex_death((void __user *)pending + futex_offset, curr, pip); + next_entry = NULL; /* avoid warning with gcc */ while (entry != (struct robust_list __user *) &head->list) { /* + * Fetch the next entry in the list before calling + * handle_futex_death: + */ + rc = fetch_robust_entry(&next_uentry, &next_entry, + (compat_uptr_t __user *)&entry->next, &next_pi); + /* * A pending lock might already be on the list, so * dont process it twice: */ @@ -74,12 +80,11 @@ void compat_exit_robust_list(struct task_struct *curr) curr, pi)) return; - /* - * Fetch the next entry in the list: - */ - if (fetch_robust_entry(&uentry, &entry, - (compat_uptr_t __user *)&entry->next, &pi)) + if (rc) return; + uentry = next_uentry; + entry = next_entry; + pi = next_pi; /* * Avoid excessively long or circular lists: */ @@ -88,6 +93,9 @@ void compat_exit_robust_list(struct task_struct *curr) cond_resched(); } + if (pending) + handle_futex_death((void __user *)pending + futex_offset, + curr, pip); } asmlinkage long |