linux-kernel - [PATCH v6 1/1] soc: qcom: mdt_loader: Enhance split binary detection

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Date:   Mon, 8 May 2023 17:18:21 -0700
From:   Gokul krishna Krishnakumar <quic_gokukris@...cinc.com>
To:     <linux-arm-msm@...r.kernel.org>
CC:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        "Satya Durga Srinivasu Prabhala" <quic_satyap@...cinc.com>,
        Rajendra Nayak <quic_rjendra@...cinc.com>,
        Elliot Berman <quic_eberman@...cinc.com>,
        "Guru Das Srinagesh" <quic_gurus@...cinc.com>,
        Sibi Sankar <quic_sibis@...cinc.com>,
        Melody Olvera <quic_molvera@...cinc.com>,
        Gokul krishna Krishnakumar <quic_gokukris@...cinc.com>
Subject: [PATCH v6 1/1] soc: qcom: mdt_loader: Enhance split binary detection

It may be that the offset of the first program header lies inside the mdt's
filesize, in this case the loader would incorrectly assume that the bins
were not split and in this scenario the firmware authentication fails.
This change updates the logic used by the mdt loader to understand whether
the firmware images are split or not. It figures this out by checking if
each programs header's segment lies within the file or not.

Co-developed-by: Melody Olvera <quic_molvera@...cinc.com>
Signed-off-by: Melody Olvera <quic_molvera@...cinc.com>
Signed-off-by: Gokul krishna Krishnakumar <quic_gokukris@...cinc.com>

---
V6: Fixed format error in qcom_mdt_bins_are_split function definition and
Correcting the s-o-b by keeping Melody as the co-developer.

V5: Removes extra empty lines from V4 and fixed the S-o-b by keeping Melody's
name first.

V4: Change the commit text to include the scenario in which we see the problem.

V3: separated out from [1] and includes changes addressing comments
from that patch set: 
	1. Change the checking condition for non-split firmwares to
	(phr->p_filesz && !issplit) on line #352 for better readability.
	2. Removes an unncecessary check for split bins in qcom_mdt_read_metadata()/

[1] https://lore.kernel.org/all/20230306231202.12223-5-quic_molvera@quicinc.com/
---
 drivers/soc/qcom/mdt_loader.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/drivers/soc/qcom/mdt_loader.c b/drivers/soc/qcom/mdt_loader.c
index 3f11554df2f3..0e35d29b4438 100644
--- a/drivers/soc/qcom/mdt_loader.c
+++ b/drivers/soc/qcom/mdt_loader.c
@@ -258,6 +258,26 @@ int qcom_mdt_pas_init(struct device *dev, const struct firmware *fw,
 }
 EXPORT_SYMBOL_GPL(qcom_mdt_pas_init);
 
+static bool qcom_mdt_bins_are_split(const struct firmware *fw, const char *fw_name)
+{
+	const struct elf32_phdr *phdrs;
+	const struct elf32_hdr *ehdr;
+	uint64_t seg_start, seg_end;
+	int i;
+
+	ehdr = (struct elf32_hdr *)fw->data;
+	phdrs = (struct elf32_phdr *)(ehdr + 1);
+
+	for (i = 0; i < ehdr->e_phnum; i++) {
+		seg_start = phdrs[i].p_offset;
+		seg_end = phdrs[i].p_offset + phdrs[i].p_filesz;
+		if (seg_start > fw->size || seg_end > fw->size)
+			return true;
+	}
+
+	return false;
+}
+
 static int __qcom_mdt_load(struct device *dev, const struct firmware *fw,
 			   const char *fw_name, int pas_id, void *mem_region,
 			   phys_addr_t mem_phys, size_t mem_size,
@@ -270,6 +290,7 @@ static int __qcom_mdt_load(struct device *dev, const struct firmware *fw,
 	phys_addr_t min_addr = PHYS_ADDR_MAX;
 	ssize_t offset;
 	bool relocate = false;
+	bool is_split;
 	void *ptr;
 	int ret = 0;
 	int i;
@@ -277,6 +298,7 @@ static int __qcom_mdt_load(struct device *dev, const struct firmware *fw,
 	if (!fw || !mem_region || !mem_phys || !mem_size)
 		return -EINVAL;
 
+	is_split = qcom_mdt_bins_are_split(fw, fw_name);
 	ehdr = (struct elf32_hdr *)fw->data;
 	phdrs = (struct elf32_phdr *)(ehdr + 1);
 
@@ -330,8 +352,7 @@ static int __qcom_mdt_load(struct device *dev, const struct firmware *fw,
 
 		ptr = mem_region + offset;
 
-		if (phdr->p_filesz && phdr->p_offset < fw->size &&
-		    phdr->p_offset + phdr->p_filesz <= fw->size) {
+		if (phdr->p_filesz && !is_split) {
 			/* Firmware is large enough to be non-split */
 			if (phdr->p_offset + phdr->p_filesz > fw->size) {
 				dev_err(dev, "file %s segment %d would be truncated\n",
-- 
2.40.1