..Add Shakeel's new email address
* Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> [240913 10:31]:
> * 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
> >
