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Thu, 05 Mar 2026 18:05:55 -0800 (PST) Date: Fri, 6 Mar 2026 10:00:12 +0800 From: Coiby Xu To: Baoquan He Cc: Thorsten Blum , Andrew Morton , Vivek Goyal , Dave Young , stable@vger.kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] crash_dump: Don't log dm-crypt key bytes in read_key_from_user_keying Message-ID: References: <20260227230008.858641-2-thorsten.blum@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: On Mon, Mar 02, 2026 at 11:48:22AM +0800, Baoquan He wrote: >On 02/28/26 at 12:00am, Thorsten Blum wrote: >> When debug logging is enabled, read_key_from_user_keying() logs the >> first 8 bytes of the key payload and partially exposes the dm-crypt key. >> Stop logging any key bytes. >> >> Fixes: 479e58549b0f ("crash_dump: store dm crypt keys in kdump reserved memory") >> Cc: stable@vger.kernel.org >> Signed-off-by: Thorsten Blum >> --- >> kernel/crash_dump_dm_crypt.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c >> index 27a144920562..5ce958d069dd 100644 >> --- a/kernel/crash_dump_dm_crypt.c >> +++ b/kernel/crash_dump_dm_crypt.c >> @@ -168,8 +168,8 @@ static int read_key_from_user_keying(struct dm_crypt_key *dm_key) >> >> memcpy(dm_key->data, ukp->data, ukp->datalen); >> dm_key->key_size = ukp->datalen; >> - kexec_dprintk("Get dm crypt key (size=%u) %s: %8ph\n", dm_key->key_size, >> - dm_key->key_desc, dm_key->data); >> + kexec_dprintk("Get dm crypt key (size=%u) %s\n", dm_key->key_size, > >Make sense to me. > >The kexec_dprintk() is only for debug printing. We can remove above line >or change it to pr_debug() if security is worried. > >Coiby, what do you think? I think we can assume a key can be reliably read thus no need to print the first 8 bytes to check it. So this patch looks good to me. And thanks to Thorsten for suggesting multiple improvements on kernel/crash_dump_dm_crypt.c! > >Thanks >Baoquan > -- Best regards, Coiby