From: Matthew Wilcox (Oracle) willy@infradead.org
commit 69a37a8ba1b408a1c7616494aa7018e4b3844cbe upstream.
If xas_split_alloc() fails to allocate the necessary nodes to complete the xarray entry split, it sets the xa_state to -ENOMEM, which xas_nomem() then interprets as "Please allocate more memory", not as "Please free any unnecessary memory" (which was the intended outcome). It's confusing to use xas_nomem() to free memory in this context, so call xas_destroy() instead.
Reported-by: syzbot+9e27a75a8c24f3fe75c1@syzkaller.appspotmail.com Fixes: 6b24ca4a1a8d ("mm: Use multi-index entries in the page cache") Cc: stable@vger.kernel.org Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/xarray.h | 1 + lib/xarray.c | 5 +++-- mm/huge_memory.c | 3 +-- 3 files changed, 5 insertions(+), 4 deletions(-)
--- a/include/linux/xarray.h +++ b/include/linux/xarray.h @@ -1506,6 +1506,7 @@ void *xas_find_marked(struct xa_state *, void xas_init_marks(const struct xa_state *);
bool xas_nomem(struct xa_state *, gfp_t); +void xas_destroy(struct xa_state *); void xas_pause(struct xa_state *);
void xas_create_range(struct xa_state *); --- a/lib/xarray.c +++ b/lib/xarray.c @@ -264,9 +264,10 @@ static void xa_node_free(struct xa_node * xas_destroy() - Free any resources allocated during the XArray operation. * @xas: XArray operation state. * - * This function is now internal-only. + * Most users will not need to call this function; it is called for you + * by xas_nomem(). */ -static void xas_destroy(struct xa_state *xas) +void xas_destroy(struct xa_state *xas) { struct xa_node *next, *node = xas->xa_alloc;
--- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2736,8 +2736,7 @@ out_unlock: if (mapping) i_mmap_unlock_read(mapping); out: - /* Free any memory we didn't use */ - xas_nomem(&xas, 0); + xas_destroy(&xas); count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED); return ret; }