github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-11-07 06:17:02 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

selftests/mm: mremap_test: Validate the preamble region before mapping it

Browse Source 
remap_region() checks that the destination region is free before mapping
it, but not the preamble region placed right before it, so mapping the
preamble can intermittently fail with EEXIST:

  # Failed to map dest preamble region: File exists
  not ok 15 5MB mremap - Source 1MB-aligned, Dest 1MB-aligned with 40MB Preamble

This happens when the kernel's heap ASLR (arch_randomize_brk()) lands the
process heap inside that unchecked range.  Confirmed by correlating
brk(NULL) at startup with pass/fail across 60 runs: every failure had brk
land inside that range.

Fix it by including the preamble in the free-region check.

Link: https://lore.kernel.org/20261014-selftests-mm-mremap_preamble-v1-1-2e97f501cb56@marliere.net
Signed-off-by: Ricardo B. Marlière (SUSE) <ricardo@marliere.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Sarthak Sharma <sarthak.sharma@arm.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shuah Khan <shuah@kernel.org>
This commit is contained in:
Ricardo B. Marlière (SUSE) 2026-10-14 15:46:46 -03:00 committed by Andrew Morton
parent 6d06041c83
commit 4425c67300
1 changed files with 4 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
tools/testing/selftests/mm/mremap_test.c
View File

@ -1006,8 +1006,10 @@ static long long remap_region(struct config c, unsigned int threshold_mb,
if (!((unsigned long long) addr & c.dest_alignment))
addr = (void *) ((unsigned long long) addr | c.dest_alignment);
/* Don't destroy existing mappings unless expected to overlap */
while (!is_remap_region_valid(addr, c.region_size) && !c.overlapping) {
/* Don't destroy existing mappings unless expected to overlap. */
while (!is_remap_region_valid(addr - c.dest_preamble_size,
c.dest_preamble_size + c.region_size) &&
!c.overlapping) {
/* Check for unsigned overflow */
tmp_addr = addr + c.dest_alignment;
if (tmp_addr < addr) {