linux-kernel - [PATCH 4.9 05/50] efi/cper: use stack buffer for error record decoding

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Date:   Mon, 25 Oct 2021 21:13:52 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Joe Perches <joe@...ches.com>,
        Ard Biesheuvel <ardb@...nel.org>
Subject: [PATCH 4.9 05/50] efi/cper: use stack buffer for error record decoding

From: Ard Biesheuvel <ardb@...nel.org>

commit b3a72ca80351917cc23f9e24c35f3c3979d3c121 upstream.

Joe reports that using a statically allocated buffer for converting CPER
error records into human readable text is probably a bad idea. Even
though we are not aware of any actual issues, a stack buffer is clearly
a better choice here anyway, so let's move the buffer into the stack
frames of the two functions that refer to it.

Cc: <stable@...r.kernel.org>
Reported-by: Joe Perches <joe@...ches.com>
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/firmware/efi/cper.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/firmware/efi/cper.c
+++ b/drivers/firmware/efi/cper.c
@@ -35,8 +35,6 @@
 
 #define INDENT_SP	" "
 
-static char rcd_decode_str[CPER_REC_LEN];
-
 /*
  * CPER record ID need to be unique even after reboot, because record
  * ID is used as index for ERST storage, while CPER records from
@@ -293,6 +291,7 @@ const char *cper_mem_err_unpack(struct t
 				struct cper_mem_err_compact *cmem)
 {
 	const char *ret = trace_seq_buffer_ptr(p);
+	char rcd_decode_str[CPER_REC_LEN];
 
 	if (cper_mem_err_location(cmem, rcd_decode_str))
 		trace_seq_printf(p, "%s", rcd_decode_str);
@@ -307,6 +306,7 @@ static void cper_print_mem(const char *p
 	int len)
 {
 	struct cper_mem_err_compact cmem;
+	char rcd_decode_str[CPER_REC_LEN];
 
 	/* Don't trust UEFI 2.1/2.2 structure with bad validation bits */
 	if (len == sizeof(struct cper_sec_mem_err_old) &&