linux-hardening - [PATCH 1/3] usercopy: Handle vm_map

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Date:   Sun, 12 Jun 2022 22:32:25 +0100
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-mm@...ck.org, Uladzislau Rezki <urezki@...il.com>,
        Zorro Lang <zlang@...hat.com>, linux-xfs@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: [PATCH 1/3] usercopy: Handle vm_map_ram() areas

vmalloc does not allocate a vm_struct for vm_map_ram() areas.  That causes
us to deny usercopies from those areas.  This affects XFS which uses
vm_map_ram() for its directories.

Fix this by calling find_vmap_area() instead of find_vm_area().

Fixes: 0aef499f3172 ("mm/usercopy: Detect vmalloc overruns")
Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 include/linux/vmalloc.h | 1 +
 mm/usercopy.c           | 8 +++++---
 mm/vmalloc.c            | 2 +-
 3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index b159c2789961..096d48aa3437 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -215,6 +215,7 @@ extern struct vm_struct *__get_vm_area_caller(unsigned long size,
 void free_vm_area(struct vm_struct *area);
 extern struct vm_struct *remove_vm_area(const void *addr);
 extern struct vm_struct *find_vm_area(const void *addr);
+struct vmap_area *find_vmap_area(unsigned long addr);
 
 static inline bool is_vm_area_hugepages(const void *addr)
 {
diff --git a/mm/usercopy.c b/mm/usercopy.c
index baeacc735b83..fdd1bed3b90a 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -173,7 +173,7 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
 	}
 
 	if (is_vmalloc_addr(ptr)) {
-		struct vm_struct *area = find_vm_area(ptr);
+		struct vmap_area *area = find_vmap_area((unsigned long)ptr);
 		unsigned long offset;
 
 		if (!area) {
@@ -181,8 +181,10 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
 			return;
 		}
 
-		offset = ptr - area->addr;
-		if (offset + n > get_vm_area_size(area))
+		/* XXX: We should also abort for free vmap_areas */
+
+		offset = (unsigned long)ptr - area->va_start;
+		if ((unsigned long)ptr + n > area->va_end)
 			usercopy_abort("vmalloc", NULL, to_user, offset, n);
 		return;
 	}
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 07db42455dd4..effd1ff6a4b4 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1798,7 +1798,7 @@ static void free_unmap_vmap_area(struct vmap_area *va)
 	free_vmap_area_noflush(va);
 }
 
-static struct vmap_area *find_vmap_area(unsigned long addr)
+struct vmap_area *find_vmap_area(unsigned long addr)
 {
 	struct vmap_area *va;
 
-- 
2.35.1