Re: [PATCH 6/7] lkdtm: crash on overwriting protected pmalloc var
On 3/7/18 5:18 AM, Igor Stoppa wrote: On 06/03/18 19:20, J Freyensee wrote: On 2/28/18 12:06 PM, Igor Stoppa wrote: [...] void __init lkdtm_perms_init(void); void lkdtm_WRITE_RO(void); void lkdtm_WRITE_RO_AFTER_INIT(void); +void lkdtm_WRITE_RO_PMALLOC(void); Does this need some sort of #ifdef too? Not strictly. It's just a function declaration. As long as it is not used, the linker will not complain. The #ifdef placed around the use and definition is sufficient, from a correctness perspective. But it's a different question if there is any standard in linux about hiding also the declaration. I'd prefer hiding it if it's contents are being ifdef'ed out, but I really think it's more of a maintainer preference question. I am not very fond of #ifdefs, so when I can I try to avoid them.
Re: [PATCH 6/7] lkdtm: crash on overwriting protected pmalloc var
On 06/03/18 19:20, J Freyensee wrote: > On 2/28/18 12:06 PM, Igor Stoppa wrote: [...] >> void __init lkdtm_perms_init(void); >> void lkdtm_WRITE_RO(void); >> void lkdtm_WRITE_RO_AFTER_INIT(void); >> +void lkdtm_WRITE_RO_PMALLOC(void); > > Does this need some sort of #ifdef too? Not strictly. It's just a function declaration. As long as it is not used, the linker will not complain. The #ifdef placed around the use and definition is sufficient, from a correctness perspective. But it's a different question if there is any standard in linux about hiding also the declaration. I am not very fond of #ifdefs, so when I can I try to avoid them. >> +pr_info("attempting bad pmalloc write at %p\n", i); >> +*i = 0; > > OK, now I'm on the right version of this patch series, same comment > applies. I don't get the local *i assignment at the end of the > function, but seems harmless. Because that's the whole point of the function: prove that pmalloc protection works (see the message in the pr_info one line above). The function is supposed to do: * create a pool * allocate memory from it * protect it * try to alter it (and crash) *i = 0; performs the last step -- igor
Re: [PATCH 6/7] lkdtm: crash on overwriting protected pmalloc var
On 2/28/18 12:06 PM, Igor Stoppa wrote: Verify that pmalloc read-only protection is in place: trying to overwrite a protected variable will crash the kernel. Signed-off-by: Igor Stoppa --- drivers/misc/lkdtm.h | 1 + drivers/misc/lkdtm_core.c | 3 +++ drivers/misc/lkdtm_perms.c | 28 3 files changed, 32 insertions(+) diff --git a/drivers/misc/lkdtm.h b/drivers/misc/lkdtm.h index 9e513dcfd809..dcda3ae76ceb 100644 --- a/drivers/misc/lkdtm.h +++ b/drivers/misc/lkdtm.h @@ -38,6 +38,7 @@ void lkdtm_READ_BUDDY_AFTER_FREE(void); void __init lkdtm_perms_init(void); void lkdtm_WRITE_RO(void); void lkdtm_WRITE_RO_AFTER_INIT(void); +void lkdtm_WRITE_RO_PMALLOC(void); Does this need some sort of #ifdef too? void lkdtm_WRITE_KERN(void); void lkdtm_EXEC_DATA(void); void lkdtm_EXEC_STACK(void); diff --git a/drivers/misc/lkdtm_core.c b/drivers/misc/lkdtm_core.c index 2154d1bfd18b..c9fd42bda6ee 100644 --- a/drivers/misc/lkdtm_core.c +++ b/drivers/misc/lkdtm_core.c @@ -155,6 +155,9 @@ static const struct crashtype crashtypes[] = { CRASHTYPE(ACCESS_USERSPACE), CRASHTYPE(WRITE_RO), CRASHTYPE(WRITE_RO_AFTER_INIT), +#ifdef CONFIG_PROTECTABLE_MEMORY + CRASHTYPE(WRITE_RO_PMALLOC), +#endif CRASHTYPE(WRITE_KERN), CRASHTYPE(REFCOUNT_INC_OVERFLOW), CRASHTYPE(REFCOUNT_ADD_OVERFLOW), diff --git a/drivers/misc/lkdtm_perms.c b/drivers/misc/lkdtm_perms.c index 53b85c9d16b8..0ac9023fd2b0 100644 --- a/drivers/misc/lkdtm_perms.c +++ b/drivers/misc/lkdtm_perms.c @@ -9,6 +9,7 @@ #include #include #include +#include #include /* Whether or not to fill the target memory area with do_nothing(). */ @@ -104,6 +105,33 @@ void lkdtm_WRITE_RO_AFTER_INIT(void) *ptr ^= 0xabcd1234; } +#ifdef CONFIG_PROTECTABLE_MEMORY +void lkdtm_WRITE_RO_PMALLOC(void) +{ + struct gen_pool *pool; + int *i; + + pool = pmalloc_create_pool("pool", 0); + if (unlikely(!pool)) { + pr_info("Failed preparing pool for pmalloc test."); + return; + } + + i = (int *)pmalloc(pool, sizeof(int), GFP_KERNEL); + if (unlikely(!i)) { + pr_info("Failed allocating memory for pmalloc test."); + pmalloc_destroy_pool(pool); + return; + } + + *i = INT_MAX; + pmalloc_protect_pool(pool); + + pr_info("attempting bad pmalloc write at %p\n", i); + *i = 0; OK, now I'm on the right version of this patch series, same comment applies. I don't get the local *i assignment at the end of the function, but seems harmless. Except the two minor comments, otherwise, Reviewed-by: Jay Freyensee +} +#endif + void lkdtm_WRITE_KERN(void) { size_t size;
Re: [PATCH 6/7] lkdtm: crash on overwriting protected pmalloc var
On 3/6/18 9:05 AM, J Freyensee wrote: +#ifdef CONFIG_PROTECTABLE_MEMORY +void lkdtm_WRITE_RO_PMALLOC(void) +{ + struct gen_pool *pool; + int *i; + + pool = pmalloc_create_pool("pool", 0); + if (unlikely(!pool)) { + pr_info("Failed preparing pool for pmalloc test."); + return; + } + + i = (int *)pmalloc(pool, sizeof(int), GFP_KERNEL); + if (unlikely(!i)) { + pr_info("Failed allocating memory for pmalloc test."); + pmalloc_destroy_pool(pool); + return; + } + + *i = INT_MAX; + pmalloc_protect_pool(pool); + + pr_info("attempting bad pmalloc write at %p\n", i); + *i = 0; Opps, disregard this, this is the last series of this patch series, not the most recent one :-(. Seems harmless, but I don't get why *i local variable needs to be set to 0 at the end of this function. Otherwise, Reviewed-by: Jay Freyensee
Re: [PATCH 6/7] lkdtm: crash on overwriting protected pmalloc var
+#ifdef CONFIG_PROTECTABLE_MEMORY +void lkdtm_WRITE_RO_PMALLOC(void) +{ + struct gen_pool *pool; + int *i; + + pool = pmalloc_create_pool("pool", 0); + if (unlikely(!pool)) { + pr_info("Failed preparing pool for pmalloc test."); + return; + } + + i = (int *)pmalloc(pool, sizeof(int), GFP_KERNEL); + if (unlikely(!i)) { + pr_info("Failed allocating memory for pmalloc test."); + pmalloc_destroy_pool(pool); + return; + } + + *i = INT_MAX; + pmalloc_protect_pool(pool); + + pr_info("attempting bad pmalloc write at %p\n", i); + *i = 0; Seems harmless, but I don't get why *i local variable needs to be set to 0 at the end of this function. Otherwise, Reviewed-by: Jay Freyensee
Re: [PATCH 6/7] lkdtm: crash on overwriting protected pmalloc var
Hi Igor, Thank you for the patch! Yet something to improve: [auto build test ERROR on linus/master] [also build test ERROR on v4.16-rc2] [cannot apply to next-20180223] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system] url: https://github.com/0day-ci/linux/commits/Igor-Stoppa/genalloc-track-beginning-of-allocations/20180225-081601 config: x86_64-rhel (attached as .config) compiler: gcc-7 (Debian 7.3.0-1) 7.3.0 reproduce: # save the attached .config to linux build tree make ARCH=x86_64 All errors (new ones prefixed by >>): >> ERROR: "pmalloc" [drivers/misc/lkdtm.ko] undefined! >> ERROR: "pmalloc_create_pool" [drivers/misc/lkdtm.ko] undefined! >> ERROR: "pmalloc_destroy_pool" [drivers/misc/lkdtm.ko] undefined! >> ERROR: "pmalloc_protect_pool" [drivers/misc/lkdtm.ko] undefined! --- 0-DAY kernel test infrastructureOpen Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation .config.gz Description: application/gzip