lib/alloc_tag: fix RCU imbalance in pgalloc_tag_get()

put_page_tag_ref() should be called only when get_page_tag_ref() returns a
valid reference because only in that case get_page_tag_ref() enters RCU
read section while put_page_tag_ref() will call rcu_read_unlock() even if
the provided reference is NULL.  Fix pgalloc_tag_get() which does not
follow this rule causing RCU imbalance.  Add a warning in
put_page_tag_ref() to catch any future mistakes.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: cc92eba1c88b ("mm: fix non-compound multi-order memory accounting in __free_pages")
Signed-off-by: Suren Baghdasaryan <[email protected]>
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-lkp/[email protected]
Acked-by: Vlastimil Babka <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Pasha Tatashin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions