[Crash-utility] [PATCH v2] Basic support for PaX's split module layout
HAGIO KAZUHITO(萩尾 一仁)
k-hagio-ab at nec.com
Fri Aug 21 08:13:44 UTC 2020
-----Original Message-----
> PaX and grsecurity kernels split module memory into dedicated r/x and
> r/w mappings using '*_rw' and '*_rx' named member variables in 'struct
> module'. To add basic support for such kernels detect the split layout
> by testing for the corresponding structure members and use these
> instead.
>
> So far we limit ourself to only track module code mappings for such
> kernels as adding support for separate data mappings violates lots of
> invariants in the rest of our code base, thereby would require a major
> rework. However, with that patch applied, module code references can be
> resolved in backtraces, memory and code dumps, which makes it already
> very useful for analyzing such kernels.
>
> Signed-off-by: Mathias Krause <minipli at grsecurity.net>
> ---
> v2:
> - add members to end of struct offset_table
> - add offsets to dump_offset_table()
>
> defs.h | 13 +++++++++++
> kernel.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++----
> symbols.c | 63 +++++++++++++++++++++++++++++++++------------------
> 3 files changed, 117 insertions(+), 27 deletions(-)
>
> diff --git a/defs.h b/defs.h
> index 17e98763362b..ae860448ab15 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -654,12 +654,15 @@ struct new_utsname {
> #define TIMER_BASES (0x20ULL)
> #define IRQ_DESC_TREE_RADIX (0x40ULL)
> #define IRQ_DESC_TREE_XARRAY (0x80ULL)
> +#define KMOD_PAX (0x100ULL)
>
> #define XEN() (kt->flags & ARCH_XEN)
> #define OPENVZ() (kt->flags & ARCH_OPENVZ)
> #define PVOPS() (kt->flags & ARCH_PVOPS)
> #define PVOPS_XEN() (kt->flags & ARCH_PVOPS_XEN)
>
> +#define PAX_MODULE_SPLIT() (kt->flags2 & KMOD_PAX)
> +
> #define XEN_MACHINE_TO_MFN(m) ((ulonglong)(m) >> PAGESHIFT())
> #define XEN_PFN_TO_PSEUDO(p) ((ulonglong)(p) << PAGESHIFT())
>
> @@ -2089,6 +2092,14 @@ struct offset_table { /* stash of commonly-used offsets */
> long size_class_size;
> long gendisk_private_data;
> long zram_table_entry;
> + long module_core_size_rw;
> + long module_core_size_rx;
> + long module_init_size_rw;
> + long module_init_size_rx;
> + long module_module_core_rw;
> + long module_module_core_rx;
> + long module_module_init_rw;
> + long module_module_init_rx;
> };
>
> struct size_table { /* stash of commonly-used sizes */
> @@ -2313,6 +2324,8 @@ struct array_table {
> * in the offset table, size table or array_table.
> */
> #define OFFSET(X) (OFFSET_verify(offset_table.X, (char *)__FUNCTION__, __FILE__, __LINE__, #X))
> +#define MODULE_OFFSET(X,Y) (PAX_MODULE_SPLIT() ? OFFSET(Y) : OFFSET(X))
> +#define MODULE_OFFSET2(X,T) MODULE_OFFSET(X, X##_##T)
> #define SIZE(X) (SIZE_verify(size_table.X, (char *)__FUNCTION__, __FILE__, __LINE__, #X))
> #define INVALID_OFFSET (-1)
> #define INVALID_MEMBER(X) (offset_table.X == INVALID_OFFSET)
> diff --git a/kernel.c b/kernel.c
> index f179375f2d3d..f0268adccd4a 100644
> --- a/kernel.c
> +++ b/kernel.c
> @@ -3540,6 +3540,62 @@ module_init(void)
> "module_core");
> MEMBER_OFFSET_INIT(module_module_init, "module",
> "module_init");
> + } else if (MEMBER_EXISTS("module", "module_core_rx")) {
> + if (CRASHDEBUG(1))
> + error(INFO, "PaX module layout detected.\n");
> + kt->flags2 |= KMOD_PAX;
> +
> + MEMBER_OFFSET_INIT(module_core_size_rw, "module",
> + "core_size_rw");
> + MEMBER_OFFSET_INIT(module_core_size_rx, "module",
> + "core_size_rx");
> +
> + MEMBER_OFFSET_INIT(module_init_size_rw, "module",
> + "init_size_rw");
> + MEMBER_OFFSET_INIT(module_init_size_rx, "module",
> + "init_size_rx");
> +
> + MEMBER_OFFSET_INIT(module_module_core_rw, "module",
> + "module_core_rw");
> + MEMBER_OFFSET_INIT(module_module_core_rx, "module",
> + "module_core_rx");
> +
> + MEMBER_OFFSET_INIT(module_module_init_rw, "module",
> + "module_init_rw");
> + MEMBER_OFFSET_INIT(module_module_init_rx, "module",
> + "module_init_rx");
> + } else if (MEMBER_EXISTS("module_layout", "base_rx")) {
> + if (CRASHDEBUG(1))
> + error(INFO, "PaX module layout detected.\n");
> + kt->flags2 |= KMOD_PAX;
> +
> + ASSIGN_OFFSET(module_core_size_rw) =
> + MEMBER_OFFSET("module", "core_layout") +
> + MEMBER_OFFSET("module_layout", "size_rw");
> + ASSIGN_OFFSET(module_core_size_rx) =
> + MEMBER_OFFSET("module", "core_layout") +
> + MEMBER_OFFSET("module_layout", "size_rx");
> +
> + ASSIGN_OFFSET(module_init_size_rw) =
> + MEMBER_OFFSET("module", "init_layout") +
> + MEMBER_OFFSET("module_layout", "size_rw");
> + ASSIGN_OFFSET(module_init_size_rx) =
> + MEMBER_OFFSET("module", "init_layout") +
> + MEMBER_OFFSET("module_layout", "size_rx");
> +
> + ASSIGN_OFFSET(module_module_core_rw) =
> + MEMBER_OFFSET("module", "core_layout") +
> + MEMBER_OFFSET("module_layout", "base_rw");
> + ASSIGN_OFFSET(module_module_core_rx) =
> + MEMBER_OFFSET("module", "core_layout") +
> + MEMBER_OFFSET("module_layout", "base_rx");
> +
> + ASSIGN_OFFSET(module_module_init_rw) =
> + MEMBER_OFFSET("module", "init_layout") +
> + MEMBER_OFFSET("module_layout", "base_rw");
> + ASSIGN_OFFSET(module_module_init_rx) =
> + MEMBER_OFFSET("module", "init_layout") +
> + MEMBER_OFFSET("module_layout", "base_rx");
> } else {
> ASSIGN_OFFSET(module_core_size) =
> MEMBER_OFFSET("module", "core_layout") +
> @@ -3682,10 +3738,10 @@ module_init(void)
> case KALLSYMS_V2:
> if (THIS_KERNEL_VERSION >= LINUX(2,6,27)) {
> numksyms = UINT(modbuf + OFFSET(module_num_symtab));
> - size = UINT(modbuf + OFFSET(module_core_size));
> + size = UINT(modbuf + MODULE_OFFSET2(module_core_size, rx));
> } else {
> numksyms = ULONG(modbuf + OFFSET(module_num_symtab));
> - size = ULONG(modbuf + OFFSET(module_core_size));
> + size = ULONG(modbuf + MODULE_OFFSET2(module_core_size, rx));
> }
>
> if (!size) {
> @@ -3792,7 +3848,7 @@ verify_modules(void)
> break;
> case KMOD_V2:
> mod_base = ULONG(modbuf +
> - OFFSET(module_module_core));
> + MODULE_OFFSET2(module_module_core, rx));
> break;
> }
>
> @@ -3816,10 +3872,10 @@ verify_modules(void)
> OFFSET(module_name);
> if (THIS_KERNEL_VERSION >= LINUX(2,6,27))
> mod_size = UINT(modbuf +
> - OFFSET(module_core_size));
> + MODULE_OFFSET2(module_core_size, rx));
> else
> mod_size = ULONG(modbuf +
> - OFFSET(module_core_size));
> + MODULE_OFFSET2(module_core_size, rx));
> if (strlen(module_name) < MAX_MOD_NAME)
> strcpy(buf, module_name);
> else
> @@ -5997,6 +6053,8 @@ dump_kernel_table(int verbose)
> fprintf(fp, "%sIRQ_DESC_TREE_RADIX", others++ ? "|" : "");
> if (kt->flags2 & IRQ_DESC_TREE_XARRAY)
> fprintf(fp, "%sIRQ_DESC_TREE_XARRAY", others++ ? "|" : "");
> + if (kt->flags2 & KMOD_PAX)
> + fprintf(fp, "%sKMOD_PAX", others++ ? "|" : "");
> fprintf(fp, ")\n");
>
> fprintf(fp, " stext: %lx\n", kt->stext);
> diff --git a/symbols.c b/symbols.c
> index 2fecaee093a2..9a80e8a585d1 100644
> --- a/symbols.c
> +++ b/symbols.c
> @@ -1766,17 +1766,17 @@ store_module_symbols_v2(ulong total, int mods_installed)
>
> if (THIS_KERNEL_VERSION >= LINUX(2,6,27)) {
> nksyms = UINT(modbuf + OFFSET(module_num_symtab));
> - size = UINT(modbuf + OFFSET(module_core_size));
> + size = UINT(modbuf + MODULE_OFFSET2(module_core_size, rx));
> } else {
> nksyms = ULONG(modbuf + OFFSET(module_num_symtab));
> - size = ULONG(modbuf + OFFSET(module_core_size));
> + size = ULONG(modbuf + MODULE_OFFSET2(module_core_size, rx));
> }
>
> mod_name = modbuf + OFFSET(module_name);
>
> lm = &st->load_modules[m++];
> BZERO(lm, sizeof(struct load_module));
> - lm->mod_base = ULONG(modbuf + OFFSET(module_module_core));
> + lm->mod_base = ULONG(modbuf + MODULE_OFFSET2(module_module_core, rx));
> lm->module_struct = mod;
> lm->mod_size = size;
> if (strlen(mod_name) < MAX_MOD_NAME)
> @@ -1795,23 +1795,23 @@ store_module_symbols_v2(ulong total, int mods_installed)
> lm->mod_flags = MOD_EXT_SYMS;
> lm->mod_ext_symcnt = mcnt;
> lm->mod_init_module_ptr = ULONG(modbuf +
> - OFFSET(module_module_init));
> + MODULE_OFFSET2(module_module_init, rx));
> if (VALID_MEMBER(module_percpu))
> lm->mod_percpu = ULONG(modbuf + OFFSET(module_percpu));
> if (THIS_KERNEL_VERSION >= LINUX(2,6,27)) {
> lm->mod_etext_guess = lm->mod_base +
> - UINT(modbuf + OFFSET(module_core_text_size));
> + UINT(modbuf + MODULE_OFFSET(module_core_text_size, module_core_size_rx));
> lm->mod_init_size =
> - UINT(modbuf + OFFSET(module_init_size));
> + UINT(modbuf + MODULE_OFFSET2(module_init_size, rx));
> lm->mod_init_text_size =
> - UINT(modbuf + OFFSET(module_init_text_size));
> + UINT(modbuf + MODULE_OFFSET(module_init_text_size, module_init_size_rx));
> } else {
> lm->mod_etext_guess = lm->mod_base +
> - ULONG(modbuf + OFFSET(module_core_text_size));
> + ULONG(modbuf + MODULE_OFFSET(module_core_text_size, module_core_size_rx));
> lm->mod_init_size =
> - ULONG(modbuf + OFFSET(module_init_size));
> + ULONG(modbuf + MODULE_OFFSET2(module_init_size, rx));
> lm->mod_init_text_size =
> - ULONG(modbuf + OFFSET(module_init_text_size));
> + ULONG(modbuf + MODULE_OFFSET(module_init_text_size, module_init_size_rx));
> }
> lm->mod_text_start = lm->mod_base;
>
> @@ -9113,18 +9113,37 @@ dump_offset_table(char *spec, ulong makestruct)
> OFFSET(module_num_gpl_syms));
> fprintf(fp, " module_list: %ld\n",
> OFFSET(module_list));
> - fprintf(fp, " module_module_core: %ld\n",
> - OFFSET(module_module_core));
> - fprintf(fp, " module_core_size: %ld\n",
> - OFFSET(module_core_size));
> - fprintf(fp, " module_core_text_size: %ld\n",
> - OFFSET(module_core_text_size));
> - fprintf(fp, " module_init_size: %ld\n",
> - OFFSET(module_init_size));
> - fprintf(fp, " module_init_text_size: %ld\n",
> - OFFSET(module_init_text_size));
> - fprintf(fp, " module_module_init: %ld\n",
> - OFFSET(module_module_init));
> + if (PAX_MODULE_SPLIT()) {
> + fprintf(fp, " module_module_core_rx: %ld\n",
> + OFFSET(module_module_core_rx));
> + fprintf(fp, " module_module_core_rw: %ld\n",
> + OFFSET(module_module_core_rw));
> + fprintf(fp, " module_core_size_rx: %ld\n",
> + OFFSET(module_core_size_rx));
> + fprintf(fp, " module_core_size_rw: %ld\n",
> + OFFSET(module_core_size_rw));
> + fprintf(fp, " module_module_init_rx: %ld\n",
> + OFFSET(module_module_init_rx));
> + fprintf(fp, " module_module_init_rw: %ld\n",
> + OFFSET(module_module_init_rw));
> + fprintf(fp, " module_init_size_rx: %ld\n",
> + OFFSET(module_init_size_rx));
> + fprintf(fp, " module_init_size_rw: %ld\n",
> + OFFSET(module_init_size_rw));
> + } else {
> + fprintf(fp, " module_module_core: %ld\n",
> + OFFSET(module_module_core));
> + fprintf(fp, " module_core_size: %ld\n",
> + OFFSET(module_core_size));
> + fprintf(fp, " module_core_text_size: %ld\n",
> + OFFSET(module_core_text_size));
> + fprintf(fp, " module_init_size: %ld\n",
> + OFFSET(module_init_size));
> + fprintf(fp, " module_init_text_size: %ld\n",
> + OFFSET(module_init_text_size));
> + fprintf(fp, " module_module_init: %ld\n",
> + OFFSET(module_module_init));
> + }
I would prefer dumping all of the defined offsets unconditionally a little
rather than this conditional switch, because they are kind of debugging
information for checking if crash is working intendedly, so I think it's
important to be able to also confirm they are "-1" certainly even if not used.
In this patch's case, obviously they will be "-1" and not used, so might not
need to be shown, but I would not like to make a precedent for future cases.
Thanks,
Kazu
> fprintf(fp, " module_num_symtab: %ld\n",
> OFFSET(module_num_symtab));
> fprintf(fp, " module_symtab: %ld\n",
> --
> 2.20.1
>
>
> --
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