linux-kernel - Re: [PATCH v8 6/7] x86/crash: pass dm crypt keys to kdump kernel

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <fa6uyhukjfjgteptdpud6wd6w7yin466p3tp6rdxwbsuqgkfdc@jwgf5ztb2ni7>
Date: Wed, 23 Apr 2025 22:59:06 +0200
From: Arnaud Lefebvre <arnaud.lefebvre@...ver-cloud.com>
To: Coiby Xu <coxu@...hat.com>
Cc: kexec@...ts.infradead.org, Ondrej Kozina <okozina@...hat.com>, 
	Milan Broz <gmazyland@...il.com>, Thomas Staudt <tstaudt@...ibm.com>, 
	Daniel P . Berrangé <berrange@...hat.com>, Kairui Song <ryncsn@...il.com>, 
	Pingfan Liu <kernelfans@...il.com>, Baoquan He <bhe@...hat.com>, Dave Young <dyoung@...hat.com>, 
	linux-kernel@...r.kernel.org, x86@...nel.org, Dave Hansen <dave.hansen@...el.com>, 
	Vitaly Kuznetsov <vkuznets@...hat.com>, Vivek Goyal <vgoyal@...hat.com>, 
	Jonathan Corbet <corbet@....net>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, 
	"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v8 6/7] x86/crash: pass dm crypt keys to kdump kernel

>diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
>index 68530fad05f7..5604a5109858 100644
>--- a/arch/x86/kernel/kexec-bzimage64.c
>+++ b/arch/x86/kernel/kexec-bzimage64.c
>@@ -76,6 +76,10 @@ static int setup_cmdline(struct kimage *image, struct boot_params *params,
> 	if (image->type == KEXEC_TYPE_CRASH) {
> 		len = sprintf(cmdline_ptr,
> 			"elfcorehdr=0x%lx ", image->elf_load_addr);
>+
>+		if (image->dm_crypt_keys_addr != 0)
>+			len += sprintf(cmdline_ptr + len,
>+					"dmcryptkeys=0x%lx ", image->dm_crypt_keys_addr);
> 	}
> 	memcpy(cmdline_ptr + len, cmdline, cmdline_len);
> 	cmdline_len += len;

You are adding another kernel parameter but I believe without taking its
length into account. See the MAX_ELFCOREHDR_STR_LEN constant which is added to the
params_cmdline_sz variable for the elfcorehdr= parameter.

This will (at least during my tests) truncate the cmdline given to the crash kernel because
the next section (efi_map_offset) will have an offset starting inside the cmdline section
and it might overwrite the end of it:

kexec-bzimage64.c:480:
params_cmdline_sz = sizeof(struct boot_params) + cmdline_len +
			MAX_ELFCOREHDR_STR_LEN; <<< Should have + 31 here for "dmcryptkeys=0x<ptr> "
params_cmdline_sz = ALIGN(params_cmdline_sz, 16);
kbuf.bufsz = params_cmdline_sz + ALIGN(efi_map_sz, 16) +
			sizeof(struct setup_data) +
			sizeof(struct efi_setup_data) +
			sizeof(struct setup_data) +
			RNG_SEED_LENGTH;

And I believe the buffer might be too small.

Also, there is another check a few lines above that needs to take the size into account:

/*
  * In case of crash dump, we will append elfcorehdr=<addr> to
  * command line. Make sure it does not overflow
  */
if (cmdline_len + MAX_ELFCOREHDR_STR_LEN > header->cmdline_size) {
	pr_err("Appending elfcorehdr=<addr> to command line exceeds maximum allowed length\n");
	return ERR_PTR(-EINVAL);
}