The following commit has been merged into the x86/mm branch of tip: Commit-ID: fd5935f9c20431eeadd6993fd4d2672e3e17a6b8 Gitweb: https://git.kernel.org/tip/fd5935f9c20431eeadd6993fd4d2672e3e17a6b8 Author: Philip Redkin <me@xxxxxxxxxx> AuthorDate: Fri, 15 Nov 2024 20:36:59 +03:00 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitterDate: Fri, 28 Feb 2025 18:02:10 +01:00 x86/mm: Check return value from memblock_phys_alloc_range() At least with CONFIG_PHYSICAL_START=0x100000, if there is < 4 MiB of contiguous free memory available at this point, the kernel will crash and burn because memblock_phys_alloc_range() returns 0 on failure, which leads memblock_phys_free() to throw the first 4 MiB of physical memory to the wolves. At a minimum it should fail gracefully with a meaningful diagnostic, but in fact everything seems to work fine without the weird reserve allocation. Signed-off-by: Philip Redkin <me@xxxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Link: https://lore.kernel.org/r/94b3e98f-96a7-3560-1f76-349eb95ccf7f@xxxxxxxxxx --- arch/x86/mm/init.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index 62aa4d6..bfa444a 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -645,8 +645,13 @@ static void __init memory_map_top_down(unsigned long map_start, */ addr = memblock_phys_alloc_range(PMD_SIZE, PMD_SIZE, map_start, map_end); - memblock_phys_free(addr, PMD_SIZE); - real_end = addr + PMD_SIZE; + if (!addr) { + pr_warn("Failed to release memory for alloc_low_pages()"); + real_end = max(map_start, ALIGN_DOWN(map_end, PMD_SIZE)); + } else { + memblock_phys_free(addr, PMD_SIZE); + real_end = addr + PMD_SIZE; + } /* step_size need to be small so pgt_buf from BRK could cover it */ step_size = PMD_SIZE;
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