From mboxrd@z Thu Jan 1 00:00:00 1970 From: mark.rutland@arm.com (Mark Rutland) Date: Fri, 5 Dec 2014 12:20:16 +0000 Subject: [PATCH] arm: mm: dump: don't skip final region Message-ID: <1417782016-11825-1-git-send-email-mark.rutland@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org If the final page table entry we walk is a valid mapping, the page table dumping code will not log the region this entry is part of, as the final note_page call in walk_pgd will trigger an early return. Luckily this isn't seen on contemporary systems as they typically don't have enough RAM to extend the linear mapping right to the end of the address space. In note_page, we log a region when we reach its end (i.e. we hit an entry immediately afterwards which has different prot bits or is invalid). The final entry has no subsequent entry, so we will not log this immediately. We try to cater for this with a subsequent call to note_page in ptdump_show, but this returns early as 0 is less than USER_PGTABLES_CEILING, and hence we will skip a valid mapping if it spans to the final entry we note. Luckily, the final note_page call has level == 0, while all prior calls have a non-zero level, so if we also check level we will both skip user entries and handle the final note_page call correctly. Due to the way addr is constructed in the walk_* functions, it can never be less than LOWEST_ADDR when walking the page tables, so it is not necessary to avoid dereferencing invalid table addresses. The existing checks for st->current_prot and st->marker[1].start_address are sufficient to ensure we will not print and/or dereference garbage when trying to log information. This patch adds the aformentioned check for level, ensuring we log all regions in the kernel mappings, including those which span right to the end of the address space. Signed-off-by: Mark Rutland Cc: Kees Cook Cc: Russell King Cc: Steve Capper Cc: Will Deacon --- arch/arm/mm/dump.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) I found this via inspection, rather than being hit by the problem described above, but it seemed worthwhile to fix this up (otherwise the final note_page call is pointless). diff --git a/arch/arm/mm/dump.c b/arch/arm/mm/dump.c index 5942493..f459c0d 100644 --- a/arch/arm/mm/dump.c +++ b/arch/arm/mm/dump.c @@ -220,7 +220,7 @@ static void note_page(struct pg_state *st, unsigned long addr, unsigned level, u static const char units[] = "KMGTPE"; u64 prot = val & pg_level[level].mask; - if (addr < USER_PGTABLES_CEILING) + if (level && addr < USER_PGTABLES_CEILING) return; if (!st->level) { -- 1.9.1