* Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> [240913 10:06]:
> In commit 96cfe2c0fd23 ("mm/madvise: replace ptrace attach requirement for
> process_madvise") process_madvise() was updated to require the caller to
> possess the CAP_SYS_NICE capability to perform the operation, in addition
> to a check against PTRACE_MODE_READ performed by mm_access().
>
> The mm_access() function explicitly checks to see if the address space of
> the process being referenced is the current one, in which case no check is
> performed.
>
> We, however, do not do this when checking the CAP_SYS_NICE capability. This
> means that we insist on the caller possessing this capability in order to
> perform madvise() operations on its own address space, which seems
> nonsensical.
>
> Simply add a check to allow for an invocation of this function with pidfd
> set to the current process without elevation.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Probably needs a fixes 96cfe2c0fd23 tag?
Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
> ---
> mm/madvise.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 4e64770be16c..ff139e57cca2 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -1520,7 +1520,7 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
> * Require CAP_SYS_NICE for influencing process performance. Note that
> * only non-destructive hints are currently supported.
> */
> - if (!capable(CAP_SYS_NICE)) {
> + if (mm != current->mm && !capable(CAP_SYS_NICE)) {
> ret = -EPERM;
> goto release_mm;
> }
> --
> 2.46.0
>
