[PATCH 6.19 068/844] EFI/CPER: don't go past the ARM processor CPER record buffer

[Sasha Levin]

From: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>

[ Upstream commit eae21beecb95a3b69ee5c38a659f774e171d730e ]

There's a logic inside GHES/CPER to detect if the section_length
is too small, but it doesn't detect if it is too big.

Currently, if the firmware receives an ARM processor CPER record
stating that a section length is big, kernel will blindly trust
section_length, producing a very long dump. For instance, a 67
bytes record with ERR_INFO_NUM set 46198 and section length
set to 854918320 would dump a lot of data going a way past the
firmware memory-mapped area.

Fix it by adding a logic to prevent it to go past the buffer
if ERR_INFO_NUM is too big, making it report instead:

	[Hardware Error]: Hardware error from APEI Generic Hardware Error Source: 1
	[Hardware Error]: event severity: recoverable
	[Hardware Error]:  Error 0, type: recoverable
	[Hardware Error]:   section_type: ARM processor error
	[Hardware Error]:   MIDR: 0xff304b2f8476870a
	[Hardware Error]:   section length: 854918320, CPER size: 67
	[Hardware Error]:   section length is too big
	[Hardware Error]:   firmware-generated error record is incorrect
	[Hardware Error]:   ERR_INFO_NUM is 46198

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>
Reviewed-by: Jonathan Cameron <jonathan.cameron@xxxxxxxxxx>
Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Reviewed-by: Hanjun Guo <guohanjun@xxxxxxxxxx>
[ rjw: Subject and changelog tweaks ]
Link: https://patch.msgid.link/41cd9f6b3ace3cdff7a5e864890849e4b1c58b63.1767871950.git.mchehab+huawei@xxxxxxxxxx
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/firmware/efi/cper-arm.c | 12 ++++++++----
 drivers/firmware/efi/cper.c     |  3 ++-
 include/linux/cper.h            |  3 ++-
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/firmware/efi/cper-arm.c b/drivers/firmware/efi/cper-arm.c
index 76542a53e2027..b21cb1232d820 100644
--- a/drivers/firmware/efi/cper-arm.c
+++ b/drivers/firmware/efi/cper-arm.c
@@ -226,7 +226,8 @@ static void cper_print_arm_err_info(const char *pfx, u32 type,
 }
 
 void cper_print_proc_arm(const char *pfx,
-			 const struct cper_sec_proc_arm *proc)
+			 const struct cper_sec_proc_arm *proc,
+			 u32 length)
 {
 	int i, len, max_ctx_type;
 	struct cper_arm_err_info *err_info;
@@ -238,9 +239,12 @@ void cper_print_proc_arm(const char *pfx,
 
 	len = proc->section_length - (sizeof(*proc) +
 		proc->err_info_num * (sizeof(*err_info)));
-	if (len < 0) {
-		printk("%ssection length: %d\n", pfx, proc->section_length);
-		printk("%ssection length is too small\n", pfx);
+
+	if (len < 0 || proc->section_length > length) {
+		printk("%ssection length: %d, CPER size: %d\n",
+		       pfx, proc->section_length, length);
+		printk("%ssection length is too %s\n", pfx,
+		       (len < 0) ? "small" : "big");
 		printk("%sfirmware-generated error record is incorrect\n", pfx);
 		printk("%sERR_INFO_NUM is %d\n", pfx, proc->err_info_num);
 		return;
diff --git a/drivers/firmware/efi/cper.c b/drivers/firmware/efi/cper.c
index 09a4f0168df80..06b4fdb59917a 100644
--- a/drivers/firmware/efi/cper.c
+++ b/drivers/firmware/efi/cper.c
@@ -664,7 +664,8 @@ cper_estatus_print_section(const char *pfx, struct acpi_hest_generic_data *gdata
 
 		printk("%ssection_type: ARM processor error\n", newpfx);
 		if (gdata->error_data_length >= sizeof(*arm_err))
-			cper_print_proc_arm(newpfx, arm_err);
+			cper_print_proc_arm(newpfx, arm_err,
+					    gdata->error_data_length);
 		else
 			goto err_section_too_small;
 #endif
diff --git a/include/linux/cper.h b/include/linux/cper.h
index 5b1236d8c65bb..440b35e459e53 100644
--- a/include/linux/cper.h
+++ b/include/linux/cper.h
@@ -595,7 +595,8 @@ void cper_mem_err_pack(const struct cper_sec_mem_err *,
 const char *cper_mem_err_unpack(struct trace_seq *,
 				struct cper_mem_err_compact *);
 void cper_print_proc_arm(const char *pfx,
-			 const struct cper_sec_proc_arm *proc);
+			 const struct cper_sec_proc_arm *proc,
+			 u32 length);
 void cper_print_proc_ia(const char *pfx,
 			const struct cper_sec_proc_ia *proc);
 int cper_mem_err_location(struct cper_mem_err_compact *mem, char *msg);
-- 
2.51.0