The process_madvise() system call is expected to skip holes in vma passed through 'struct iovec' vector list. But do_madvise, which process_madvise() calls for each vma, returns ENOMEM in case of unmapped holes, despite the VMA is processed. Thus process_madvise() should treat ENOMEM as expected and consider the VMA passed to as processed and continue processing other vma's in the vector list. Returning -ENOMEM to user, despite the VMA is processed, will be unable to figure out where to start the next madvise.
Fixes: ecb8ac8b1f14("mm/madvise: introduce process_madvise() syscall: an external memory hinting API") Cc: stable@vger.kernel.org # 5.10+ Signed-off-by: Charan Teja Kalla quic_charante@quicinc.com --- Changes in V2: -- Fixed handling of ENOMEM by process_madvise(). -- Patch doesn't exist in V1.
mm/madvise.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/mm/madvise.c b/mm/madvise.c index e97e6a9..14fb76d 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1426,9 +1426,16 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
while (iov_iter_count(&iter)) { iovec = iov_iter_iovec(&iter); + /* + * do_madvise returns ENOMEM if unmapped holes are present + * in the passed VMA. process_madvise() is expected to skip + * unmapped holes passed to it in the 'struct iovec' list + * and not fail because of them. Thus treat -ENOMEM return + * from do_madvise as valid and continue processing. + */ ret = do_madvise(mm, (unsigned long)iovec.iov_base, iovec.iov_len, behavior); - if (ret < 0) + if (ret < 0 && ret != -ENOMEM) break; iov_iter_advance(&iter, iovec.iov_len); }