Reviewed-by: Marvin Häuser > On 27. Jan 2023, at 15:22, Pedro Falcato wrote: > > On Fri, Jan 27, 2023 at 9:29 AM Savva Mitrofanov > 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 >> Cc: Pedro Falcato >> Cc: Vitaly Cheptsov >> Fixes: d9ceedca6c8f ("Ext4Pkg: Add Ext4Dxe driver.") >> Signed-off-by: Savva Mitrofanov >> --- >> 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