Re: [PATCH] x86/vdso: fix incorrect size in munmap during map_vdso failure

[Thomas Weißschuh]

On Sun, May 03, 2026 at 04:16:09PM -0300, Guilherme Giacomo Simoes wrote:
> In the map_vdso function, if a failure occurs during the installation of
> the VVAR mappings, the error path attempts to clean up previously
> allocated mappings using do_munmap. However, the cleanup for the VVAR
> mapping was incorrectly using image->size (the size of the vDSO text)
> instead of the actual size allocated for the VVAR area.
> 
> Replace the incorrect image->size parameter with the constant
> VDSO_NR_PAGES * PAGE_SIZE in the do_munmap call. Ensure the unmap size
> exactly matches the size used during the vdso_install_vvar_mapping()
> phase to provide a symmetrical and complete teardown of the memory
> region.

Out of curiosity, did you encounter this in the real world?

> Signed-off-by: Guilherme Giacomo Simoes <trintaeoitogc@xxxxxxxxx>

Fixes: e93d2521b27f ("x86/vdso: Split virtual clock pages into dedicated mapping")
Reviewed-by: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>

> ---
>  arch/x86/entry/vdso/vma.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
> index a6bfcc8243cd..d903bce24f15 100644
> --- a/arch/x86/entry/vdso/vma.c
> +++ b/arch/x86/entry/vdso/vma.c
> @@ -178,7 +178,7 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr)
>  	if (IS_ERR(vma)) {
>  		ret = PTR_ERR(vma);
>  		do_munmap(mm, text_start, image->size, NULL);
> -		do_munmap(mm, addr, image->size, NULL);
> +		do_munmap(mm, addr, VDSO_NR_PAGES * PAGE_SIZE, NULL);
>  		goto up_fail;
>  	}
>  
> -- 
> 2.52.0
>