On Tue, 2020-01-07 at 10:26 -0800, Kees Cook wrote: > From: Aleksandr Yashkin <a.yashkin@xxxxxxxxxxxxxxxxxx> > > [ Upstream commit 9e5f1c19800b808a37fb9815a26d382132c26c3d ] This looks applicable to 3.16 as well, so I've queued it up. Ben. > 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") > [kees: backport to v4.9] > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > --- > fs/pstore/ram.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c > index 59d93acc29c7..fa0e89edb62d 100644 > --- a/fs/pstore/ram.c > +++ b/fs/pstore/ram.c > @@ -319,6 +319,17 @@ static int notrace ramoops_pstore_write_buf(enum pstore_type_id type, > > prz = cxt->przs[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); > + > hlen = ramoops_write_kmsg_hdr(prz, compressed); > if (size + hlen > prz->buffer_size) > size = prz->buffer_size - hlen; > -- > 2.20.1 > > -- Ben Hutchings The program is absolutely right; therefore, the computer must be wrong.
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