Messages in this thread Patch in this message | | | Date | Mon, 19 Apr 2021 10:52:02 +0200 | From | Borislav Petkov <> | Subject | Re: [patch] x86/crash: fix crash_setup_memmap_entries() out-of-bounds access |
| |
Here's an attempt to explain what this fixes:
--- From: Mike Galbraith <efault@gmx.de> Date: Fri, 16 Apr 2021 14:02:07 +0200 Subject: [PATCH] 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> Link: https://lkml.kernel.org/r/725fa3dc1da2737f0f6188a1a9701bead257ea9d.camel@gmx.de --- 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 a8f3af257e26..b1deacbeb266 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; -- 2.29.2 -- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
| |