On Fri, Jan 27, 2023 at 9:29 AM Savva Mitrofanov <savva...@gmail.com> wrote: > > Missing check for wrong s_log_block_size exponent leads to shift out of > bounds. Limit block size to 2 MiB > > Cc: Marvin Häuser <mhaeu...@posteo.de> > Cc: Pedro Falcato <pedro.falc...@gmail.com> > Cc: Vitaly Cheptsov <vit9...@protonmail.com> > Fixes: d9ceedca6c8f ("Ext4Pkg: Add Ext4Dxe driver.") > Signed-off-by: Savva Mitrofanov <savva...@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 2e489ce4dd86..a23323319a59 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. Nit: s/page size/large page size/ I can change this for you when pushing, no need for a v4 on this one. > +// 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 be3527e4d618..3f56de93c105 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 > -- > 2.39.0 >
Reviewed-by: Pedro Falcato <pedro.falc...@gmail.com> -- Pedro -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#99166): https://edk2.groups.io/g/devel/message/99166 Mute This Topic: https://groups.io/mt/96562695/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-