[PATCH v11 3/7] alloc_tag: clean up the populate failure path

[Hao Ge]

The reservation is already stored in the maple tree when
vm_module_tags_populate() fails. A failed load never unloads the
module, so nothing releases the entry. Release it and roll
module_tags.size back. Without the rollback a concurrent load that
already passed needs_section_mem() can reuse the freed gap, skip
vm_module_tags_populate() and write to unmapped memory.

Fixes: 4835f747d3ed ("alloc_tag: support for page allocation tag compression")
Fixes: 0f9b685626da ("alloc_tag: populate memory for module tags as needed")
Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Hao Ge <hao.ge@xxxxxxxxx>
---
 mm/alloc_tag.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/alloc_tag.c b/mm/alloc_tag.c
index 2070e682fe10..3e6306ee0764 100644
--- a/mm/alloc_tag.c
+++ b/mm/alloc_tag.c
@@ -947,6 +947,7 @@ static void *reserve_module_tags(struct module *mod, unsigned long size,
 		return ret;
 
 	if (module_tags.size < offset + size) {
+		unsigned long prev_size = module_tags.size;
 		int grow_res;
 
 		module_tags.size = offset + size;
@@ -961,6 +962,8 @@ static void *reserve_module_tags(struct module *mod, unsigned long size,
 			shutdown_mem_profiling(true);
 			pr_err("Failed to allocate memory for allocation tags in the module %s. Memory allocation profiling is disabled!\n",
 			       mod->name);
+			release_module_tags(mod, false);
+			module_tags.size = prev_size;
 			return ERR_PTR(grow_res);
 		}
 	}
-- 
2.25.1