Commit 24bd843b authored by Lorenzo Stoakes's avatar Lorenzo Stoakes Committed by Andrew Morton
Browse files

mm: enforce __must_check on VMA merge and split 

It is of critical importance to check the return results on VMA merge (and
split), failure to do so can result in use-after-free's.  This bug has
recurred, so have the compiler enforce this check to prevent any future
repetition.

Link: https://lkml.kernel.org/r/20241206225036.273103-1-lorenzo.stoakes@oracle.com


Signed-off-by: default avatarLorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: default avatarLiam R. Howlett <Liam.Howlett@Oracle.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 79dc2bff

mm/vma.c

+5 −3
Original line number Diff line number Diff line
@@ -447,7 +447,8 @@ void unmap_region(struct ma_state *mas, struct vm_area_struct *vma, 
 * has already been checked or doesn't make sense to fail.

 * VMA Iterator will point to the original VMA.

 */

static int __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,

static __must_check int

__split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,

	    unsigned long addr, int new_below)

{

	struct vma_prepare vp;
@@ -710,7 +711,8 @@ static bool can_merge_remove_vma(struct vm_area_struct *vma) 
 * - The caller must hold a WRITE lock on the mm_struct->mmap_lock.

 * - vmi must be positioned within [@vmg->vma->vm_start, @vmg->vma->vm_end).

 */

static struct vm_area_struct *vma_merge_existing_range(struct vma_merge_struct *vmg)

static __must_check struct vm_area_struct *vma_merge_existing_range(

		struct vma_merge_struct *vmg)

{

	struct vm_area_struct *vma = vmg->vma;

	struct vm_area_struct *prev = vmg->prev;

mm/vma.h

+15 −11
Original line number Diff line number Diff line
@@ -139,8 +139,9 @@ void validate_mm(struct mm_struct *mm); 
#define validate_mm(mm) do { } while (0)

#endif



int vma_expand(struct vma_merge_struct *vmg);

int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma,

__must_check int vma_expand(struct vma_merge_struct *vmg);

__must_check int vma_shrink(struct vma_iterator *vmi,

		struct vm_area_struct *vma,

		unsigned long start, unsigned long end, pgoff_t pgoff);



static inline int vma_iter_store_gfp(struct vma_iterator *vmi,
@@ -174,13 +175,14 @@ void unmap_region(struct ma_state *mas, struct vm_area_struct *vma, 
		struct vm_area_struct *prev, struct vm_area_struct *next);



/* We are about to modify the VMA's flags. */

struct vm_area_struct *vma_modify_flags(struct vma_iterator *vmi,

__must_check struct vm_area_struct

*vma_modify_flags(struct vma_iterator *vmi,

		struct vm_area_struct *prev, struct vm_area_struct *vma,

		unsigned long start, unsigned long end,

		unsigned long new_flags);



/* We are about to modify the VMA's flags and/or anon_name. */

struct vm_area_struct

__must_check struct vm_area_struct

*vma_modify_flags_name(struct vma_iterator *vmi,

		       struct vm_area_struct *prev,

		       struct vm_area_struct *vma,
@@ -190,7 +192,7 @@ struct vm_area_struct 
		       struct anon_vma_name *new_name);



/* We are about to modify the VMA's memory policy. */

struct vm_area_struct

__must_check struct vm_area_struct

*vma_modify_policy(struct vma_iterator *vmi,

		   struct vm_area_struct *prev,

		   struct vm_area_struct *vma,
@@ -198,7 +200,7 @@ struct vm_area_struct 
		   struct mempolicy *new_pol);



/* We are about to modify the VMA's flags and/or uffd context. */

struct vm_area_struct

__must_check struct vm_area_struct

*vma_modify_flags_uffd(struct vma_iterator *vmi,

		       struct vm_area_struct *prev,

		       struct vm_area_struct *vma,
@@ -206,9 +208,11 @@ struct vm_area_struct 
		       unsigned long new_flags,

		       struct vm_userfaultfd_ctx new_ctx);



struct vm_area_struct *vma_merge_new_range(struct vma_merge_struct *vmg);

__must_check struct vm_area_struct

*vma_merge_new_range(struct vma_merge_struct *vmg);



struct vm_area_struct *vma_merge_extend(struct vma_iterator *vmi,

__must_check struct vm_area_struct

*vma_merge_extend(struct vma_iterator *vmi,

		  struct vm_area_struct *vma,

		  unsigned long delta);