mm/gup: adapt get_user_page_vma_remote() to never return NULL

get_user_pages_remote() will never return 0 except in the case of
FOLL_NOWAIT being specified, which we explicitly disallow.

This simplifies error handling for the caller and avoids the awkwardness
of dealing with both errors and failing to pin.  Failing to pin here is an
error.

Link: https://lkml.kernel.org/r/00319ce292d27b3aae76a0eb220ce3f528187508.1696288092.git.lstoakes@gmail.com
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index 4edecaa..8878b39 100644 (file)
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -411,8 +411,8 @@ static int __access_remote_tags(struct mm_struct *mm, unsigned long addr,
                struct page *page = get_user_page_vma_remote(mm, addr,
                                                             gup_flags, &vma);
 
-               if (IS_ERR_OR_NULL(page)) {
-                       err = page == NULL ? -EIO : PTR_ERR(page);
+               if (IS_ERR(page)) {
+                       err = PTR_ERR(page);
                        break;
                }
 

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7b89f7b..fa608cb 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2425,6 +2425,9 @@ long pin_user_pages_remote(struct mm_struct *mm,
                           unsigned int gup_flags, struct page **pages,
                           int *locked);
 
+/*
+ * Retrieves a single page alongside its VMA. Does not support FOLL_NOWAIT.
+ */
 static inline struct page *get_user_page_vma_remote(struct mm_struct *mm,
                                                    unsigned long addr,
                                                    int gup_flags,
@@ -2432,12 +2435,15 @@ static inline struct page *get_user_page_vma_remote(struct mm_struct *mm,
 {
        struct page *page;
        struct vm_area_struct *vma;
-       int got = get_user_pages_remote(mm, addr, 1, gup_flags, &page, NULL);
+       int got;
+
+       if (WARN_ON_ONCE(unlikely(gup_flags & FOLL_NOWAIT)))
+               return ERR_PTR(-EINVAL);
+
+       got = get_user_pages_remote(mm, addr, 1, gup_flags, &page, NULL);
 
        if (got < 0)
                return ERR_PTR(got);
-       if (got == 0)
-               return NULL;
 
        vma = vma_lookup(mm, addr);
        if (WARN_ON_ONCE(!vma)) {

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 3048589..435aac1 100644 (file)
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -474,8 +474,8 @@ retry:
                gup_flags |= FOLL_SPLIT_PMD;
        /* Read the page with vaddr into memory */
        old_page = get_user_page_vma_remote(mm, vaddr, gup_flags, &vma);
-       if (IS_ERR_OR_NULL(old_page))
-               return old_page ? PTR_ERR(old_page) : 0;
+       if (IS_ERR(old_page))
+               return PTR_ERR(old_page);
 
        ret = verify_opcode(old_page, vaddr, &opcode);
        if (ret <= 0)

diff --git a/mm/memory.c b/mm/memory.c
index e47c36c..1f88e4f 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5815,7 +5815,7 @@ static int __access_remote_vm(struct mm_struct *mm, unsigned long addr,
                struct page *page = get_user_page_vma_remote(mm, addr,
                                                             gup_flags, &vma);
 
-               if (IS_ERR_OR_NULL(page)) {
+               if (IS_ERR(page)) {
                        /* We might need to expand the stack to access it */
                        vma = vma_lookup(mm, addr);
                        if (!vma) {
@@ -5829,7 +5829,6 @@ static int __access_remote_vm(struct mm_struct *mm, unsigned long addr,
                                continue;
                        }
 
-
                        /*
                         * Check if this is a VM_IO | VM_PFNMAP VMA, which
                         * we can access using slightly different code.