[2/5] watch_queue: Make watch_sizeof() check record size [ver #2]
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Message ID 159645999738.1779777.4882634293182825979.stgit@warthog.procyon.org.uk
State New
Headers show
Series
  • Mount notifications [ver #2]
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Commit Message

David Howells Aug. 3, 2020, 1:06 p.m. UTC
Make watch_sizeof() give a build error if the size of the struct won't fit
into the size field in the header.

Reported-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 include/linux/watch_queue.h |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Patch
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diff --git a/include/linux/watch_queue.h b/include/linux/watch_queue.h
index 5e08db2adc31..38e04c7a7951 100644
--- a/include/linux/watch_queue.h
+++ b/include/linux/watch_queue.h
@@ -120,7 +120,12 @@  static inline void remove_watch_list(struct watch_list *wlist, u64 id)
  * watch_sizeof - Calculate the information part of the size of a watch record,
  * given the structure size.
  */
-#define watch_sizeof(STRUCT) (sizeof(STRUCT) << WATCH_INFO_LENGTH__SHIFT)
+#define watch_sizeof(STRUCT) \
+	({								\
+		size_t max = WATCH_INFO_LENGTH >> WATCH_INFO_LENGTH__SHIFT; \
+		BUILD_BUG_ON(sizeof(STRUCT) > max);			\
+		sizeof(STRUCT) << WATCH_INFO_LENGTH__SHIFT;		\
+	})
 
 #endif