From fecff1b50acd43c3d9929905dd6d94d3152aece8 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Thu, 1 Nov 2018 16:17:22 -0700 Subject: [PATCH] pstore/ram: Correctly calculate usable PRZ bytes The actual number of bytes stored in a PRZ is smaller than the bytes requested by platform data, since there is a header on each PRZ. Additionally, if ECC is enabled, there are trailing bytes used as well. Normally this mismatch doesn't matter since PRZs are circular buffers and the leading "overflow" bytes are just thrown away. However, in the case of a compressed record, this rather badly corrupts the results. This corruption was visible with "ramoops.mem_size=204800 ramoops.ecc=1". Any stored crashes would not be uncompressable (producing a pstorefs "dmesg-*.enc.z" file), and triggering errors at boot: [ 2.790759] pstore: crypto_comp_decompress failed, ret = -22! Backporting this depends on commit 64c919e44a24 ("pstore: Convert console write to use ->write_buf") Reported-by: Joel Fernandes Fixes: 1287d1e0d31d ("pstore: Add compression support to pstore") Signed-off-by: Kees Cook Reviewed-by: Joel Fernandes (Google) --- fs/pstore/ram.c | 15 ++++++--------- include/linux/pstore.h | 5 ++++- 2 files changed, 10 insertions(+), 10 deletions(-) diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c index 712960e117fea..8646fe6e916fe 100644 --- a/fs/pstore/ram.c +++ b/fs/pstore/ram.c @@ -816,17 +816,14 @@ static int ramoops_probe(struct platform_device *pdev) cxt->pstore.data = cxt; /* - * Console can handle any buffer size, so prefer LOG_LINE_MAX. If we - * have to handle dumps, we must have at least record_size buffer. And - * for ftrace, bufsize is irrelevant (if bufsize is 0, buf will be - * ZERO_SIZE_PTR). + * Since bufsize is only used for dmesg crash dumps, it + * must match the size of the dprz record (after PRZ header + * and ECC bytes have been accounted for). */ - if (cxt->console_size) - cxt->pstore.bufsize = 1024; /* LOG_LINE_MAX */ - cxt->pstore.bufsize = max(cxt->record_size, cxt->pstore.bufsize); - cxt->pstore.buf = kmalloc(cxt->pstore.bufsize, GFP_KERNEL); + cxt->pstore.bufsize = cxt->dprzs[0]->buffer_size; + cxt->pstore.buf = kzalloc(cxt->pstore.bufsize, GFP_KERNEL); if (!cxt->pstore.buf) { - pr_err("cannot allocate pstore buffer\n"); + pr_err("cannot allocate pstore crash dump buffer\n"); err = -ENOMEM; goto fail_clear; } diff --git a/include/linux/pstore.h b/include/linux/pstore.h index a15bc4d487528..30fcec375a3af 100644 --- a/include/linux/pstore.h +++ b/include/linux/pstore.h @@ -90,7 +90,10 @@ struct pstore_record { * * @buf_lock: spinlock to serialize access to @buf * @buf: preallocated crash dump buffer - * @bufsize: size of @buf available for crash dump writes + * @bufsize: size of @buf available for crash dump bytes (must match + * smallest number of bytes available for writing to a + * backend entry, since compressed bytes don't take kindly + * to being truncated) * * @read_mutex: serializes @open, @read, @close, and @erase callbacks * @flags: bitfield of frontends the backend can accept writes for -- 2.39.5