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authorPeter Zijlstra <peterz@infradead.org>2020-03-04 11:28:31 +0100
committerPeter Zijlstra <peterz@infradead.org>2020-03-06 11:06:15 +0100
commit8019ad13ef7f64be44d4f892af9c840179009254 (patch)
tree889b754b07fa844410d6782bc1b4473007a9bc99 /include
parent98d54f81e36ba3bf92172791eba5ca5bd813989b (diff)
futex: Fix inode life-time issue
As reported by Jann, ihold() does not in fact guarantee inode persistence. And instead of making it so, replace the usage of inode pointers with a per boot, machine wide, unique inode identifier. This sequence number is global, but shared (file backed) futexes are rare enough that this should not become a performance issue. Reported-by: Jann Horn <jannh@google.com> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/fs.h1
-rw-r--r--include/linux/futex.h17
2 files changed, 11 insertions, 7 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3cd4fe6b845e..abedbffe2c9e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -698,6 +698,7 @@ struct inode {
struct rcu_head i_rcu;
};
atomic64_t i_version;
+ atomic64_t i_sequence; /* see futex */
atomic_t i_count;
atomic_t i_dio_count;
atomic_t i_writecount;
diff --git a/include/linux/futex.h b/include/linux/futex.h
index 5cc3fed27d4c..b70df27d7e85 100644
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -31,23 +31,26 @@ struct task_struct;
union futex_key {
struct {
+ u64 i_seq;
unsigned long pgoff;
- struct inode *inode;
- int offset;
+ unsigned int offset;
} shared;
struct {
+ union {
+ struct mm_struct *mm;
+ u64 __tmp;
+ };
unsigned long address;
- struct mm_struct *mm;
- int offset;
+ unsigned int offset;
} private;
struct {
+ u64 ptr;
unsigned long word;
- void *ptr;
- int offset;
+ unsigned int offset;
} both;
};
-#define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = NULL } }
+#define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = 0ULL } }
#ifdef CONFIG_FUTEX
enum {