commit 98c1e69d58e76d31114fa118a5ebf08473096044
author Andrew Jeffery <andrew@aj.id.au> Wed Jun 14 14:41:19 2023 +0930
committer Andrew Jeffery <andrew@aj.id.au> Mon Jun 19 15:58:03 2023 +0930
tree 414343ca9eaeee5ae154531cf072ae07dc7d282d
parent df02e36029bede81b3c8de2b83ae33e6c1ae3d6e

bios_table: Relax pldm_bios_table_string_entry_decode_string_check()

Allow the string decoded by
pldm_bios_table_string_entry_decode_string_check() to be truncated, as
per the unchecked pldm_bios_table_string_entry_decode_string(). With
this change pldm_bios_table_string_entry_decode_string_check() provides
assert() safety but is otherwise equivalent.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: Ia872f1496c642efbb34ee3ae29455f4eaf574082

CHANGELOG.md

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e990245..b19d23e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -40,6 +40,8 @@
    To disable `oem-ibm` in your development builds, pass `-Doem-ibm=disabled`
    when invoking `meson setup`
 
+4. bios_table: Relax pldm_bios_table_string_entry_decode_string_check()
+
 ### Removed
 
 1. libpldm: Remove the requester-api option

include/libpldm/bios_table.h

diff --git a/include/libpldm/bios_table.h b/include/libpldm/bios_table.h
index 09831f4..f56b066 100644
--- a/include/libpldm/bios_table.h
+++ b/include/libpldm/bios_table.h
@@ -144,9 +144,11 @@
  *  @param[out] buffer - Pointer to a buffer to store the string
  *  @param[in] size - Size of the buffer to store the string
  *  @return PLDM_SUCCESS on success, PLDM_ERROR_INVALID_DATA if entry or buffer are NULL, or
- *          PLDM_ERROR_INVALID_LENGTH if size is insufficient for the decoded string. An
+ *          PLDM_ERROR_INVALID_LENGTH if size is insufficient for NUL termination. An
  *          appropriate value for size can be determined using the expression
- *          `pldm_bios_table_string_entry_decode_string_length(entry) + 1`.
+ *          `pldm_bios_table_string_entry_decode_string_length(entry) + 1`. The provided size value
+ *          may be smaller than the entry's string, in which case the string placed in buffer will
+ *          be truncated (but still NUL terminated).
  */
 int pldm_bios_table_string_entry_decode_string_check(
 	const struct pldm_bios_string_table_entry *entry, char *buffer,

src/bios_table.c

diff --git a/src/bios_table.c b/src/bios_table.c
index 436f3e6..d6cf6f3 100644
--- a/src/bios_table.c
+++ b/src/bios_table.c
@@ -114,9 +114,9 @@
 {
 	POINTER_CHECK(entry);
 	POINTER_CHECK(buffer);
-	size_t length =
-		pldm_bios_table_string_entry_decode_string_length(entry);
-	BUFFER_SIZE_EXPECT(size, length + 1);
+	if (size == 0) {
+		return PLDM_ERROR_INVALID_LENGTH;
+	}
 	pldm_bios_table_string_entry_decode_string(entry, buffer, size);
 	return PLDM_SUCCESS;
 }

tests/libpldm_bios_table_test.cpp

diff --git a/tests/libpldm_bios_table_test.cpp b/tests/libpldm_bios_table_test.cpp
index 4cefa30..c677b99 100644
--- a/tests/libpldm_bios_table_test.cpp
+++ b/tests/libpldm_bios_table_test.cpp
@@ -1006,9 +1006,10 @@
     EXPECT_EQ(rc, PLDM_SUCCESS);
     EXPECT_EQ(std::strcmp("Allowed", buffer.data()), 0);
 
-    rc = pldm_bios_table_string_entry_decode_string_check(entry, buffer.data(),
-                                                          buffer.size() - 1);
-    EXPECT_EQ(rc, PLDM_ERROR_INVALID_LENGTH);
+    /* Ensure equivalence with the unchecked API */
+    rc = pldm_bios_table_string_entry_decode_string_check(
+        entry, buffer.data(), 2 + 1 /* sizeof '\0' */);
+    EXPECT_EQ(rc, std::strcmp("Al", buffer.data()));
 }
 
 TEST(StringTable, IteratorTest)