In memmap_exclude_ranges(), elfheader will be excluded from crashk_res. In the current x86 architecture code, the elfheader is always allocated at crashk_res.start. It seems that there won't be a new split range. But it depends on the allocation position of elfheader in crashk_res. To avoid potential out of bounds in future, add a extra slot. And using random kexec_buf for passing dm crypt keys may cause a range split too, add another extra slot here.
The similar issue also exists in fill_up_crash_elf_data(). The range to be excluded is [0, 1M], start (0) is special and will not appear in the middle of existing cmem->ranges[]. But in cast the low 1M could be changed in the future, add a extra slot too. Previously discussed link: [1] https://lore.kernel.org/kexec/ZXk2oBf%2FT1Ul6o0c@MiWiFi-R3L-srv/ [2] https://lore.kernel.org/kexec/273284e8-7680-4f5f-8065-c5d780987...@easystack.cn/ [3] https://lore.kernel.org/kexec/ZYQ6O%2F57sHAPxTHm@MiWiFi-R3L-srv/ Signed-off-by: fuqiang wang <fuqiang.w...@easystack.cn> Signed-off-by: Baoquan He <b...@redhat.com> --- v4->v5: - This is on top of Coiby's LUKS patchset in branch mm-nonmm-unstable of akpm/mm.git. I did some adaption based on Coiby's patches. - [PATCH v9 0/8] Support kdump with LUKS encryption by reusing LUKS volume keys arch/x86/kernel/crash.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index bcb534688dfe..749a60ce8b7f 100644 --- a/arch/x86/kernel/crash.c +++ b/arch/x86/kernel/crash.c @@ -165,8 +165,18 @@ static struct crash_mem *fill_up_crash_elf_data(void) /* * Exclusion of crash region and/or crashk_low_res may cause * another range split. So add extra two slots here. + * + * Exclusion of low 1M may not cause another range split, because the + * range of exclude is [0, 1M] and the condition for splitting a new + * region is that the start, end parameters are both in a certain + * existing region in cmem and cannot be equal to existing region's + * start or end. Obviously, the start of [0, 1M] cannot meet this + * condition. + * + * But in order to lest the low 1M could be changed in the future, + * (e.g. [stare, 1M]), add a extra slot. */ - nr_ranges += 2; + nr_ranges += 3; cmem = vzalloc(struct_size(cmem, ranges, nr_ranges)); if (!cmem) return NULL; @@ -313,10 +323,15 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params) struct crash_mem *cmem; /* - * Using random kexec_buf for passing dm crypt keys may cause a range - * split. So use two slots here. + * In the current x86 architecture code, the elfheader is always + * allocated at crashk_res.start. But it depends on the allocation + * position of elfheader in crashk_res. To avoid potential out of + * bounds in future, add an extra slot. + * + * And using random kexec_buf for passing dm crypt keys may cause a + * range split too, add another extra slot here. */ - nr_ranges = 2; + nr_ranges = 3; cmem = vzalloc(struct_size(cmem, ranges, nr_ranges)); if (!cmem) return -ENOMEM; -- 2.41.0
