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. Signed-off-by: Ricardo B. Marlière (SUSE) <[email protected]> --- Hi, this sporadic issue has been found in openSUSE CI: https://openqa.opensuse.org/tests/6270334/logfile?filename=serial_terminal.txt#line-6760 --- tools/testing/selftests/mm/mremap_test.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/mm/mremap_test.c b/tools/testing/selftests/mm/mremap_test.c index 131d9d6db867..8d4fa3025a9d 100644 --- a/tools/testing/selftests/mm/mremap_test.c +++ b/tools/testing/selftests/mm/mremap_test.c @@ -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) { --- base-commit: 0fcb05b72344f40806cbe810de8872f1698bf053 change-id: 20261014-selftests-mm-mremap_preamble-5f98ad625f93 Best regards, -- Ricardo B. Marlière (SUSE) <[email protected]>
