From: "Savva Mitrofanov" <savvamtr@gmail.com>
To: devel@edk2.groups.io
Cc: "Marvin Häuser" <mhaeuser@posteo.de>,
"Pedro Falcato" <pedro.falcato@gmail.com>,
"Vitaly Cheptsov" <vit9696@protonmail.com>
Subject: [edk2-platforms][PATCH v2 07/11] Ext4Pkg: Fix shift out of bounds in Ext4OpenSuperblock
Date: Mon, 12 Dec 2022 20:46:50 +0600 [thread overview]
Message-ID: <20221212144654.2650-8-savvamtr@gmail.com> (raw)
In-Reply-To: <20221212144654.2650-1-savvamtr@gmail.com>
Missing check for wrong s_log_block_size exponent leads to shift out of
bounds. Limit block size to 2 MiB
Cc: Marvin Häuser <mhaeuser@posteo.de>
Cc: Pedro Falcato <pedro.falcato@gmail.com>
Cc: Vitaly Cheptsov <vit9696@protonmail.com>
Fixes: e55f0527dde48a5f139c1b8f35acc4e6b59dd794
Signed-off-by: Savva Mitrofanov <savvamtr@gmail.com>
---
Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h | 14 ++++++++++++++
Features/Ext4Pkg/Ext4Dxe/Superblock.c | 5 +++++
2 files changed, 19 insertions(+)
diff --git a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
index beceb9d60dcb..a7e138e99561 100644
--- a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
+++ b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
@@ -40,6 +40,20 @@
#define EXT4_EFI_PATH_MAX 4096
#define EXT4_DRIVER_VERSION 0x0000
+//
+// The EXT4 Specification doesn't strictly limit block size and this value could be up to 2^31,
+// but in practice it is limited by PAGE_SIZE due to performance significant impact.
+// Many EXT4 implementations have size of block limited to PAGE_SIZE. In many cases it's limited
+// to 4096, which is a commonly supported page size on most MMU-capable hardware, and up to 65536.
+// So, to take a balance between compatibility and security measures, it is decided to use the
+// value of 2MiB as the limit, which is equal to page size on new hardware.
+// As for supporting big block sizes, EXT4 has a RO_COMPAT_FEATURE called BIGALLOC, which changes
+// EXT4 to use clustered allocation, so that each bit in the ext4 block allocation bitmap addresses
+// a power of two number of blocks. So it would be wiser to implement and use this feature
+// if there is such a need instead of big block size.
+//
+#define EXT4_LOG_BLOCK_SIZE_MAX 11
+
/**
Opens an ext4 partition and installs the Simple File System protocol.
diff --git a/Features/Ext4Pkg/Ext4Dxe/Superblock.c b/Features/Ext4Pkg/Ext4Dxe/Superblock.c
index adaf475ea54d..ffe66a8bb847 100644
--- a/Features/Ext4Pkg/Ext4Dxe/Superblock.c
+++ b/Features/Ext4Pkg/Ext4Dxe/Superblock.c
@@ -248,6 +248,11 @@ Ext4OpenSuperblock (
return EFI_VOLUME_CORRUPTED;
}
+ if (Sb->s_log_block_size > EXT4_LOG_BLOCK_SIZE_MAX) {
+ DEBUG ((DEBUG_ERROR, "[ext4] SuperBlock s_log_block_size %lu is too big\n", Sb->s_log_block_size));
+ return EFI_UNSUPPORTED;
+ }
+
Partition->BlockSize = (UINT32)LShiftU64 (1024, Sb->s_log_block_size);
// The size of a block group can also be calculated as 8 * Partition->BlockSize
--
2.38.1
next prev parent reply other threads:[~2022-12-12 14:47 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-12 14:46 [edk2-platforms][PATCH v2 00/11] Ext4Pkg: Code correctness and security improvements Savva Mitrofanov
2022-12-12 14:46 ` [edk2-platforms][PATCH v2 01/11] Ext4Pkg: Fix memory leak in Ext4RetrieveDirent Savva Mitrofanov
2022-12-12 14:46 ` [edk2-platforms][PATCH v2 02/11] Ext4Pkg: Move EXT4_NAME_MAX definition to Ext4Disk.h Savva Mitrofanov
2022-12-12 14:46 ` [edk2-platforms][PATCH v2 03/11] Ext4Pkg: Fix global buffer overflow in Ext4ReadDir Savva Mitrofanov
2022-12-16 16:03 ` Marvin Häuser
2022-12-12 14:46 ` [edk2-platforms][PATCH v2 04/11] Ext4Pkg: Fix incorrect checksum metadata feature check Savva Mitrofanov
2022-12-12 14:46 ` [edk2-platforms][PATCH v2 05/11] Ext4Pkg: Fix division by zero by adding check for s_inodes_per_group Savva Mitrofanov
2022-12-12 14:46 ` [edk2-platforms][PATCH v2 06/11] Ext4Pkg: Add inode number validity check Savva Mitrofanov
2022-12-12 14:46 ` Savva Mitrofanov [this message]
2022-12-12 14:46 ` [edk2-platforms][PATCH v2 08/11] Ext4Pkg: Corrects integer overflow check logic in DiskUtil Savva Mitrofanov
2022-12-12 14:46 ` [edk2-platforms][PATCH v2 09/11] Ext4Pkg: Check that source file is directory in Ext4OpenInternal Savva Mitrofanov
2022-12-12 14:46 ` [edk2-platforms][PATCH v2 10/11] Ext4Pkg: Check VolumeName allocation correctness in Ext4GetVolumeName Savva Mitrofanov
2022-12-12 14:46 ` [edk2-platforms][PATCH v2 11/11] Ext4Pkg: Add missing exit Status in Ext4OpenDirent Savva Mitrofanov
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