diff options
authorSergey Senozhatsky <>2017-11-15 17:34:03 -0800
committerLinus Torvalds <>2017-11-15 18:21:03 -0800
commit1aedcafbf32b3f232c159b14cd0d423fcfe2b861 (patch)
parent0bea803e9e6bf3836d5368a6426c30a8c0e5eab5 (diff)
zsmalloc: calling zs_map_object() from irq is a bug
Use BUG_ON(in_interrupt()) in zs_map_object(). This is not a new BUG_ON(), it's always been there, but was recently changed to VM_BUG_ON(). There are several problems there. First, we use use per-CPU mappings both in zsmalloc and in zram, and interrupt may easily corrupt those buffers. Second, and more importantly, we believe it's possible to start leaking sensitive information. Consider the following case: -> process P swap out zram per-cpu mapping CPU1 compress page A -> IRQ swap out zram per-cpu mapping CPU1 compress page B write page from per-cpu mapping CPU1 to zsmalloc pool iret -> process P write page from per-cpu mapping CPU1 to zsmalloc pool [*] return * so we store overwritten data that actually belongs to another page (task) and potentially contains sensitive data. And when process P will page fault it's going to read (swap in) that other task's data. Link: Signed-off-by: Sergey Senozhatsky <> Acked-by: Minchan Kim <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 7c38e850a8fc..685049a9048d 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1349,7 +1349,7 @@ void *zs_map_object(struct zs_pool *pool, unsigned long handle,
* pools/users, we can't allow mapping in interrupt context
* because it can corrupt another users mappings.
- WARN_ON_ONCE(in_interrupt());
+ BUG_ON(in_interrupt());
/* From now on, migration cannot move the object */