From: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx> Subject: 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: http://lkml.kernel.org/r/20170929045140.4055-1-sergey.senozhatsky@xxxxxxxxx Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx> Acked-by: Minchan Kim <minchan@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/zsmalloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff -puN mm/zsmalloc.c~zsmalloc-calling-zs_map_object-from-irq-is-a-bug mm/zsmalloc.c --- a/mm/zsmalloc.c~zsmalloc-calling-zs_map_object-from-irq-is-a-bug +++ a/mm/zsmalloc.c @@ -1349,7 +1349,7 @@ void *zs_map_object(struct zs_pool *pool * 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 */ pin_tag(handle); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
