From: Laura Abbott <labbott@xxxxxxxxxx> Subject: proc/kcore: don't bounds check against address 0 The existing kcore code checks for bad addresses against __va(0) with the assumption that this is the lowest address on the system. This may not hold true on some systems (e.g. arm64) and produce overflows and crashes. Switch to using other functions to validate the address range. It's currently only seen on arm64 and it's not clear if anyone wants to use that particular combination on a stable release. So this is not urgent for stable. Link: http://lkml.kernel.org/r/20180501201143.15121-1-labbott@xxxxxxxxxx Signed-off-by: Laura Abbott <labbott@xxxxxxxxxx> Tested-by: Dave Anderson <anderson@xxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Andi Kleen <andi@xxxxxxxxxxxxxx> Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>a Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/proc/kcore.c | 23 ++++++++++++++++------- 1 file changed, 16 insertions(+), 7 deletions(-) diff -puN fs/proc/kcore.c~proc-kcore-dont-bounds-check-against-address-0 fs/proc/kcore.c --- a/fs/proc/kcore.c~proc-kcore-dont-bounds-check-against-address-0 +++ a/fs/proc/kcore.c @@ -209,25 +209,34 @@ kclist_add_private(unsigned long pfn, un { struct list_head *head = (struct list_head *)arg; struct kcore_list *ent; + struct page *p; + + if (!pfn_valid(pfn)) + return 1; + + p = pfn_to_page(pfn); + if (!memmap_valid_within(pfn, p, page_zone(p))) + return 1; ent = kmalloc(sizeof(*ent), GFP_KERNEL); if (!ent) return -ENOMEM; - ent->addr = (unsigned long)__va((pfn << PAGE_SHIFT)); + ent->addr = (unsigned long)page_to_virt(p); ent->size = nr_pages << PAGE_SHIFT; - /* Sanity check: Can happen in 32bit arch...maybe */ - if (ent->addr < (unsigned long) __va(0)) + if (!virt_addr_valid(ent->addr)) goto free_out; /* cut not-mapped area. ....from ppc-32 code. */ if (ULONG_MAX - ent->addr < ent->size) ent->size = ULONG_MAX - ent->addr; - /* cut when vmalloc() area is higher than direct-map area */ - if (VMALLOC_START > (unsigned long)__va(0)) { - if (ent->addr > VMALLOC_START) - goto free_out; + /* + * We've already checked virt_addr_valid so we know this address + * is a valid pointer, therefore we can check against it to determine + * if we need to trim + */ + if (VMALLOC_START > ent->addr) { if (VMALLOC_START - ent->addr < ent->size) ent->size = VMALLOC_START - ent->addr; } _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
