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Fri, 01 May 2026 16:43:58 -0700 (PDT) From: Coiby Xu To: kexec@lists.infradead.org Cc: Andrew Morton , Sourabh Jain , Baoquan He , Dave Young , Mike Rapoport , Pasha Tatashin , Pratyush Yadav , Coiby Xu , linux-kernel@vger.kernel.org (open list) Subject: [PATCH v2 1/9] crash_dump: Release reference to a keyring at correct time Date: Sat, 2 May 2026 07:43:30 +0800 Message-ID: <20260501234342.2518281-2-coiby.xu@gmail.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260501234342.2518281-1-coiby.xu@gmail.com> References: <20260501234342.2518281-1-coiby.xu@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit It's incorrect to drop the reference only after adding one key to the specified keyring. If there are many keys to be added, it can lead "refcount_t: underflow; use-after-free" error and some keys will fail to be added to the keyring. My testing shows the error can occur when there are more than five keys. Fixes: 62f17d9df692 ("crash_dump: retrieve dm crypt keys in kdump kernel") Signed-off-by: Coiby Xu --- kernel/crash_dump_dm_crypt.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c index cb875ddb6ba6..eac4f436a8d4 100644 --- a/kernel/crash_dump_dm_crypt.c +++ b/kernel/crash_dump_dm_crypt.c @@ -81,7 +81,6 @@ static int add_key_to_keyring(struct dm_crypt_key *dm_key, kexec_dprintk("Error when adding key"); } - key_ref_put(keyring_ref); return r; } @@ -126,8 +125,10 @@ static int restore_dm_crypt_keys_to_thread_keyring(void) keys_header_size = get_keys_header_size(key_count); keys_header = kzalloc(keys_header_size, GFP_KERNEL); - if (!keys_header) + if (!keys_header) { + key_ref_put(keyring_ref); return -ENOMEM; + } dm_crypt_keys_read((char *)keys_header, keys_header_size, &addr); @@ -137,6 +138,7 @@ static int restore_dm_crypt_keys_to_thread_keyring(void) add_key_to_keyring(key, keyring_ref); } + key_ref_put(keyring_ref); return 0; } -- 2.54.0