The patch titled
robust futex thread exit race
has been added to the -mm tree. Its filename is
robust-futex-thread-exit-race.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: robust futex thread exit race
From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
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@xxxxxxxxxx>
Acked-by: Ingo Molnar <mingo@xxxxxxx>
Acked-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/futex.c | 26 ++++++++++++++++----------
kernel/futex_compat.c | 28 ++++++++++++++++++----------
2 files changed, 34 insertions(+), 20 deletions(-)
diff -puN kernel/futex.c~robust-futex-thread-exit-race kernel/futex.c
--- a/kernel/futex.c~robust-futex-thread-exit-race
+++ a/kernel/futex.c
@@ -1943,9 +1943,10 @@ static inline int fetch_robust_entry(str
void exit_robust_list(struct task_struct *curr)
{
struct robust_list_head __user *head = curr->robust_list;
- struct robust_list __user *entry, *pending;
- unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
+ struct robust_list __user *entry, *next_entry, *pending;
+ unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
unsigned long futex_offset;
+ int rc;
/*
* Fetch the list head (which was registered earlier, via
@@ -1965,12 +1966,14 @@ void exit_robust_list(struct task_struct
if (fetch_robust_entry(&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 != &head->list) {
/*
+ * Fetch the next entry in the list before calling
+ * handle_futex_death:
+ */
+ rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi);
+ /*
* A pending lock might already be on the list, so
* don't process it twice:
*/
@@ -1978,11 +1981,10 @@ void exit_robust_list(struct task_struct
if (handle_futex_death((void __user *)entry + futex_offset,
curr, pi))
return;
- /*
- * Fetch the next entry in the list:
- */
- if (fetch_robust_entry(&entry, &entry->next, &pi))
+ if (rc)
return;
+ entry = next_entry;
+ pi = next_pi;
/*
* Avoid excessively long or circular lists:
*/
@@ -1991,6 +1993,10 @@ void exit_robust_list(struct task_struct
cond_resched();
}
+
+ if (pending)
+ handle_futex_death((void __user *)pending + futex_offset,
+ curr, pip);
}
long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
diff -puN kernel/futex_compat.c~robust-futex-thread-exit-race kernel/futex_compat.c
--- a/kernel/futex_compat.c~robust-futex-thread-exit-race
+++ a/kernel/futex_compat.c
@@ -38,10 +38,11 @@ fetch_robust_entry(compat_uptr_t *uentry
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
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
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
cond_resched();
}
+ if (pending)
+ handle_futex_death((void __user *)pending + futex_offset,
+ curr, pip);
}
asmlinkage long
_
Patches currently in -mm which might be from schwidefsky@xxxxxxxxxx are
robust-futex-thread-exit-race.patch
slow-down-printk-during-boot-fix-4.patch
git-s390.patch
during-vm-oom-condition-kill-all-threads-in-process-group.patch
move-mm_struct-and-vm_area_struct.patch
move-mm_struct-and-vm_area_struct-fix.patch
unicode-diacritics-support-s390-fix.patch
bitops-introduce-lock-ops.patch
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