In grub-module-verifierXX.c, the function grub_module_verifyXX() performs an
initial check that the ELF section headers are within the module's size, but
doesn't check if the sections being accessed have contents that are within the
module's size. In particular, we need to check that sh_offset and sh_size are
less than the module's size. However, for some section header types we don't
need to make these checks. For the type SHT_NULL, the section header is marked
as inactive and the rest of the members within the section header have undefined
values, so we don't need to check for sh_offset or sh_size. In the case of the
type SHT_NOBITS, sh_offset has a conceptual offset which may be beyond the
module size. Also, this type's sh_size may have a non-zero size, but a section
of this type will take up no space in the module. This can all be checked in the
function get_shdr(), but in order to do so, the parameter module_size must be
added to functions so that the value of the module size can be used in
get_shdr() from grub_module_verifyXX().
Also, had to rework some for loops to ensure the index passed to get_shdr() is
within bounds.
Signed-off-by: Alec Brown <alec.r.brown@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Allow treating util/grub-module-verifierXX.c as a file you can build
directly so syntax checkers like vim's "syntastic" plugin, which uses
"gcc -x c -fsyntax-only" to build it, will work.
One still has to do whatever setup is required to make it pick the
right include dirs, which -I options we use, etc., but this makes
it so you can do the checking on the file you're editing, rather
than on a different file.
Signed-off-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Robbie Harwood <rharwood@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
In util/grub-module-verifierXX.c, the function get_shnum() returns the variable
shnum, which is of the type Elf_Word. In the function, shnum can be obtained by
the e_shnum member of an Elf_Ehdr or the sh_size member of an Elf_Shdr. The
sh_size member can either be grub_uint32_t or grub_uint64_t, depending on the
architecture, but Elf_Word is only grub_uint32_t. To account for when sh_size is
grub_uint64_t, we can set shnum to have type Elf_Shnum and have get_shnum()
return an Elf_Shnum.
Signed-off-by: Alec Brown <alec.r.brown@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
In util/grub-module-verifierXX.c, the function get_shdr() is used to obtain the
section header at a given index but isn't checking that there is an offset for
the section header table. To validate that there is, we can check that e_shoff
isn't 0.
Signed-off-by: Alec Brown <alec.r.brown@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
In grub-module-verifierXX.c, the function find_section() uses the value from
grub_target_to_host16 (e->e_shstrndx) to obtain the section header table index
of the section name string table, but it wasn't being checked if the value was
there.
According to the elf(5) manual page,
"If the index of section name string table section is larger than or equal
to SHN_LORESERVE (0xff00), this member holds SHN_XINDEX (0xffff) and the real
index of the section name string table section is held in the sh_link member of
the initial entry in section header table. Otherwise, the sh_link member of the
initial entry in section header table contains the value zero."
Since this check wasn't being made, the function get_shstrndx() is being added
to make this check and use e_shstrndx if it doesn't have SHN_XINDEX as a value,
else use sh_link. We also need to make sure e_shstrndx isn't greater than or
equal to SHN_LORESERVE and sh_link isn't less than SHN_LORESERVE.
Note that it may look as though the argument *arch isn't being used, it's
actually required in order to use the macros grub_target_to_host*(x) which are
unwinded to grub_target_to_host*_real(arch, (x)) based on defines earlier in
the file.
Signed-off-by: Alec Brown <alec.r.brown@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
In grub-module-verifierXX.c, grub_target_to_host16 (e->e_shnum) is used to
obtain the number of section header table entries, but it wasn't being
checked if the value was there.
According to the elf(5) manual page,
"If the number of entries in the section header table is larger than or equal
to SHN_LORESERVE (0xff00), e_shnum holds the value zero and the real number of
entries in the section header table is held in the sh_size member of the intial
entry in section header table. Otherwise, the sh_size member of the initial
entry in the section header table holds the value zero."
Since this check wasn't being made, the function get_shnum() is being added to
make this check and use whichever member doesn't have a value of zero. If both
are zero, then we must return an error. We also need to make sure that e_shnum
doesn't have a value greater than or equal to SHN_LORESERVE and sh_size isn't
less than SHN_LORESERVE.
Note that it may look as though the argument *arch isn't being used, it's
actually required in order to use the macros grub_target_to_host*(x) which are
unwinded to grub_target_to_host*_real(arch, (x)) based on defines earlier in
the file.
Fixes: CID 314021
Fixes: CID 314027
Fixes: CID 314033
Signed-off-by: Alec Brown <alec.r.brown@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Added the function get_shdr() which returns the section header at a given index
parameter passed into this function. This helps traverse the section header
table and reduces repeated calls to lengthy equations used to obtain section
headers.
Note that it may look as though the argument *arch isn't being used, it's
actually required in order to use the macros grub_target_to_host*(x) which are
unwinded to grub_target_to_host*_real(arch, (x)) based on defines earlier in the
file.
Signed-off-by: Alec Brown <alec.r.brown@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Make it so that when grub-module-verifier complains of an issue, it tells you
which module the issue was with.
Signed-off-by: Peter Jones <pjones@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
all_video module does not have any code or data and exists solely for
.moddeps section to pull in dependencies. This makes all symbols unneeded.
While in current binutils (last released version as of this commit is 2.26)
``strip --strip-unneeded'' unintentionally adds section symbols for each
existing section, this behavior was considered a bug and changed in commit
14f2c699ddca1e2f706342dffc59a6c7e23e844c to completely strip symbol table
in this case.
Older binutils (verified with 2.17) and some other toolchains (at least
elftoolchain r3223M), both used in FreeBSD, remove symbol table in all_video
as well.
Relax run-time check and do not return error for modules without symbol table.
Add additional checks to module verifier to make sure such modules
a) have non-empty .moddeps section. Without either externally visible symbols
or .moddeps modules are completely useless and should not be built.
b) do not have any relocations.
Closes: 46986
v2: add run-time check for empty symbol table if relocations are present as
suggested by Vladimir.
