The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 9e5f1c19800b808a37fb9815a26d382132c26c3d Mon Sep 17 00:00:00 2001 From: Aleksandr Yashkin <a.yashkin@xxxxxxxxxxxxxxxxxx> Date: Mon, 23 Dec 2019 18:38:16 +0500 Subject: [PATCH] pstore/ram: Write new dumps to start of recycled zones The ram_core.c routines treat przs as circular buffers. When writing a new crash dump, the old buffer needs to be cleared so that the new dump doesn't end up in the wrong place (i.e. at the end). The solution to this problem is to reset the circular buffer state before writing a new Oops dump. Signed-off-by: Aleksandr Yashkin <a.yashkin@xxxxxxxxxxxxxxxxxx> Signed-off-by: Nikolay Merinov <n.merinov@xxxxxxxxxxxxxxxxxx> Signed-off-by: Ariel Gilman <a.gilman@xxxxxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20191223133816.28155-1-n.merinov@xxxxxxxxxxxxxxxxxx Fixes: 896fc1f0c4c6 ("pstore/ram: Switch to persistent_ram routines") Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c index f753f3b6f88d..487ee39b438a 100644 --- a/fs/pstore/ram.c +++ b/fs/pstore/ram.c @@ -407,6 +407,17 @@ static int notrace ramoops_pstore_write(struct pstore_record *record) prz = cxt->dprzs[cxt->dump_write_cnt]; + /* + * Since this is a new crash dump, we need to reset the buffer in + * case it still has an old dump present. Without this, the new dump + * will get appended, which would seriously confuse anything trying + * to check dump file contents. Specifically, ramoops_read_kmsg_hdr() + * expects to find a dump header in the beginning of buffer data, so + * we must to reset the buffer values, in order to ensure that the + * header will be written to the beginning of the buffer. + */ + persistent_ram_zap(prz); + /* Build header and append record contents. */ hlen = ramoops_write_kmsg_hdr(prz, record); if (!hlen)
