From 6a45336b9b6fcc1d9ef3c6fe9a43252f9a20084b Mon Sep 17 00:00:00 2001 From: Suren Baghdasaryan Date: Sat, 19 Jul 2025 11:28:51 -0700 Subject: [PATCH] selftests/proc: extend /proc/pid/maps tearing test to include vma remapping MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Test that /proc/pid/maps does not report unexpected holes in the address space when we concurrently remap a part of a vma into the middle of another vma. This remapping results in the destination vma being split into three parts and the part in the middle being patched back from, all done concurrently from under the reader. We should always see either original vma or the split one with no holes. Link: https://lkml.kernel.org/r/20250719182854.3166724-4-surenb@google.com Signed-off-by: Suren Baghdasaryan Cc: Alexey Dobriyan Cc: Andrii Nakryiko Cc: Christian Brauner Cc: Christophe Leroy Cc: David Hildenbrand Cc: Jann Horn Cc: Jeongjun Park Cc: Johannes Weiner Cc: Josef Bacik Cc: Kalesh Singh Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Oscar Salvador Cc: "Paul E . McKenney" Cc: Peter Xu Cc: Ryan Roberts Cc: Shuah Khan Cc: Thomas Weißschuh Cc: T.J. Mercier Cc: Vlastimil Babka Cc: Ye Bin Signed-off-by: Andrew Morton --- tools/testing/selftests/proc/proc-maps-race.c | 86 +++++++++++++++++++ 1 file changed, 86 insertions(+) diff --git a/tools/testing/selftests/proc/proc-maps-race.c b/tools/testing/selftests/proc/proc-maps-race.c index 19028bd3b85c6..bc614a2d944aa 100644 --- a/tools/testing/selftests/proc/proc-maps-race.c +++ b/tools/testing/selftests/proc/proc-maps-race.c @@ -264,6 +264,35 @@ static inline bool check_shrink_result(struct line_content *mod_last_line, strcmp(mod_first_line->text, restored_first_line->text) == 0; } +static inline bool remap_vma(FIXTURE_DATA(proc_maps_race) *self) +{ + /* + * Remap the last page of the next vma into the middle of the vma. + * This splits the current vma and the first and middle parts (the + * parts at lower addresses) become the last vma objserved in the + * first page and the first vma observed in the last page. + */ + return mremap(self->mod_info->next_addr + self->page_size * 2, self->page_size, + self->page_size, MREMAP_FIXED | MREMAP_MAYMOVE | MREMAP_DONTUNMAP, + self->mod_info->addr + self->page_size) != MAP_FAILED; +} + +static inline bool patch_vma(FIXTURE_DATA(proc_maps_race) *self) +{ + return mprotect(self->mod_info->addr + self->page_size, self->page_size, + self->mod_info->prot) == 0; +} + +static inline bool check_remap_result(struct line_content *mod_last_line, + struct line_content *mod_first_line, + struct line_content *restored_last_line, + struct line_content *restored_first_line) +{ + /* Make sure vmas at the boundaries are changing */ + return strcmp(mod_last_line->text, restored_last_line->text) != 0 && + strcmp(mod_first_line->text, restored_first_line->text) != 0; +} + FIXTURE_SETUP(proc_maps_race) { const char *duration = getenv("DURATION"); @@ -523,4 +552,61 @@ TEST_F(proc_maps_race, test_maps_tearing_from_resize) signal_state(mod_info, TEST_DONE); } +TEST_F(proc_maps_race, test_maps_tearing_from_remap) +{ + struct vma_modifier_info *mod_info = self->mod_info; + + struct line_content remapped_last_line; + struct line_content remapped_first_line; + struct line_content restored_last_line; + struct line_content restored_first_line; + + wait_for_state(mod_info, SETUP_READY); + + /* re-read the file to avoid using stale data from previous test */ + ASSERT_TRUE(read_boundary_lines(self, &self->last_line, &self->first_line)); + + mod_info->vma_modify = remap_vma; + mod_info->vma_restore = patch_vma; + mod_info->vma_mod_check = check_remap_result; + + ASSERT_TRUE(capture_mod_pattern(self, &remapped_last_line, &remapped_first_line, + &restored_last_line, &restored_first_line)); + + /* Now start concurrent modifications for self->duration_sec */ + signal_state(mod_info, TEST_READY); + + struct line_content new_last_line; + struct line_content new_first_line; + struct timespec start_ts, end_ts; + + clock_gettime(CLOCK_MONOTONIC_COARSE, &start_ts); + do { + ASSERT_TRUE(read_boundary_lines(self, &new_last_line, &new_first_line)); + + /* Check if we read vmas after remapping it */ + if (!strcmp(new_last_line.text, remapped_last_line.text)) { + /* + * The vmas should be consistent with remap results, + * however if the vma was concurrently restored, it + * can be reported twice (first as split one, then + * as restored one) because we found it as the next vma + * again. In that case new first line will be the same + * as the last restored line. + */ + ASSERT_FALSE(strcmp(new_first_line.text, remapped_first_line.text) && + strcmp(new_first_line.text, restored_last_line.text)); + } else { + /* The vmas should be consistent with the original/resored state */ + ASSERT_FALSE(strcmp(new_last_line.text, restored_last_line.text)); + ASSERT_FALSE(strcmp(new_first_line.text, restored_first_line.text)); + } + + clock_gettime(CLOCK_MONOTONIC_COARSE, &end_ts); + } while (end_ts.tv_sec - start_ts.tv_sec < self->duration_sec); + + /* Signal the modifyer thread to stop and wait until it exits */ + signal_state(mod_info, TEST_DONE); +} + TEST_HARNESS_MAIN -- 2.47.2