Re: [PATCH v3] mm/madvise: unrestrict process_madvise() for current process

On 9/26/24 17:10, Lorenzo Stoakes wrote:

The process_madvise() call was introduced in commit ecb8ac8b1f14
("mm/madvise: introduce process_madvise() syscall: an external memory
hinting API") as a means of performing madvise() operations on another
process.

However, as it provides the means by which to perform multiple madvise()
operations in a batch via an iovec, it is useful to utilise the same
interface for performing operations on the current process rather than a
remote one.

Commit 22af8caff7d1 ("mm/madvise: process_madvise() drop capability check
if same mm") removed the need for a caller invoking process_madvise() on
its own pidfd to possess the CAP_SYS_NICE capability, however this leaves
the restrictions on operation in place.

Resolve this by only applying the restriction on operations when accessing
a remote process.

Moving forward we plan to implement a simpler means of specifying this
condition other than needing to establish a self pidfd, perhaps in the form
of a sentinel pidfd.

Also take the opportunity to refactor the system call implementation
abstracting the vectorised operation.

Signed-off-by: Lorenzo Stoakes <redacted>

Acked-by: Vlastimil Babka <redacted>

Looks like the destructive modes should work with the vectorized version
too, and with how it returns a partial success.

We'll need a man page update though, right?