The following commit has been merged into the x86/urgent branch of tip:

Commit-ID: 5849cdf8c120e3979c57d34be55b92d90a77a47e Gitweb: https://git.kernel.org/tip/5849cdf8c120e3979c57d34be55b92d90a77a47e Author: Mike Galbraith efault@gmx.de AuthorDate: Fri, 16 Apr 2021 14:02:07 +02:00 Committer: Borislav Petkov bp@suse.de CommitterDate: Tue, 20 Apr 2021 17:32:46 +02:00

x86/crash: Fix crash_setup_memmap_entries() out-of-bounds access

Commit in Fixes: added support for kexec-ing a kernel on panic using a new system call. As part of it, it does prepare a memory map for the new kernel.

However, while doing so, it wrongly accesses memory it has not allocated: it accesses the first element of the cmem->ranges[] array in memmap_exclude_ranges() but it has not allocated the memory for it in crash_setup_memmap_entries(). As KASAN reports:

BUG: KASAN: vmalloc-out-of-bounds in crash_setup_memmap_entries+0x17e/0x3a0 Write of size 8 at addr ffffc90000426008 by task kexec/1187

(gdb) list *crash_setup_memmap_entries+0x17e 0xffffffff8107cafe is in crash_setup_memmap_entries (arch/x86/kernel/crash.c:322). 317 unsigned long long mend) 318 { 319 unsigned long start, end; 320 321 cmem->ranges[0].start = mstart; 322 cmem->ranges[0].end = mend; 323 cmem->nr_ranges = 1; 324 325 /* Exclude elf header region */ 326 start = image->arch.elf_load_addr; (gdb)

Make sure the ranges array becomes a single element allocated.

[ bp: Write a proper commit message. ]

Fixes: dd5f726076cc ("kexec: support for kexec on panic using new system call") Signed-off-by: Mike Galbraith efault@gmx.de Signed-off-by: Borislav Petkov bp@suse.de Reviewed-by: Dave Young dyoung@redhat.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/725fa3dc1da2737f0f6188a1a9701bead257ea9d.camel@gmx... --- arch/x86/kernel/crash.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index a8f3af2..b1deacb 100644 --- a/arch/x86/kernel/crash.c +++ b/arch/x86/kernel/crash.c @@ -337,7 +337,7 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params) struct crash_memmap_data cmd; struct crash_mem *cmem;

- cmem = vzalloc(sizeof(struct crash_mem)); + cmem = vzalloc(struct_size(cmem, ranges, 1)); if (!cmem) return -ENOMEM;