| Message ID | 20230703215709.1195644-4-tusharsu@linux.microsoft.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | ima: measure events between kexec load and execute | expand |
Hi Tushar, The function to "ima: allocate buffer at kexec load to hold ima measurements" already exists. Please update the Subject line to indicate increasing the IMA kexec buffer size. On Mon, 2023-07-03 at 14:57 -0700, Tushar Sugandhi wrote: > The IMA subsystem needs a dedicated mechanism to reserve extra memory for > measurements added between the kexec 'load' and kexec 'execute'. What is a "dedicated mechanism?". Either start the sentence with "reserve ..." or completely remove it. > Update ima_add_kexec_buffer to allocate a buffer of a sufficient size > taking ima binary runtime measurements size, size of ima_kexec_hdr, and > IMA_KEXEC_EXTRA_SIZE into account. Adjust the kexec_segment_size to align > to the PAGE_SIZE. Call ima_allocate_buf_at_kexec_load() to allocate the > buffer. The size of the ima_kexec_hdr kind of gets lost in the amount of additional memory being allocated, but sure it's a nice clean up. > This patch assumes the extra space defined (IMA_KEXEC_EXTRA_SIZE) is > sufficient to handle the additional measurements. This should be as per > the system requirements and based on the number of additional measurements > expected during the window from kexec 'load' to kexec 'execute'. Should the extra amount of memory be hard coded? > Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com> > --- > security/integrity/ima/ima.h | 2 ++ > security/integrity/ima/ima_kexec.c | 21 ++++++++++----------- > 2 files changed, 12 insertions(+), 11 deletions(-) > > diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h > index c29db699c996..2ffda9449b9b 100644 > --- a/security/integrity/ima/ima.h > +++ b/security/integrity/ima/ima.h > @@ -43,6 +43,8 @@ enum tpm_pcrs { TPM_PCR0 = 0, TPM_PCR8 = 8, TPM_PCR10 = 10 }; > > #define NR_BANKS(chip) ((chip != NULL) ? chip->nr_allocated_banks : 0) > > +#define IMA_KEXEC_EXTRA_SIZE (16 * PAGE_SIZE) > Not all IMA policies require extra memory. Define and use a new IMA Kconfig to set the amount of extra memory. > /* current content of the policy */ > extern int ima_policy_flag; > > diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c > index 858b67689701..7deb8df31485 100644 > --- a/security/integrity/ima/ima_kexec.c > +++ b/security/integrity/ima/ima_kexec.c > @@ -188,31 +188,30 @@ void ima_add_kexec_buffer(struct kimage *image) > /* use more understandable variable names than defined in kbuf */ > void *kexec_buffer = NULL; > size_t kexec_buffer_size; > - size_t kexec_segment_size; > int ret; > > /* > - * Reserve an extra half page of memory for additional measurements > - * added during the kexec load. > + * Reserve extra memory for measurements added in the window from > + * kexec 'load' to kexec 'execute'. > */ > - binary_runtime_size = ima_get_binary_runtime_size(); > + binary_runtime_size = ima_get_binary_runtime_size() + > + sizeof(struct ima_kexec_hdr) + > + IMA_KEXEC_EXTRA_SIZE; > + > if (binary_runtime_size >= ULONG_MAX - PAGE_SIZE) > kexec_segment_size = ULONG_MAX; > else > - kexec_segment_size = ALIGN(ima_get_binary_runtime_size() + > - PAGE_SIZE / 2, PAGE_SIZE); > + kexec_segment_size = ALIGN(binary_runtime_size, PAGE_SIZE); > + > if ((kexec_segment_size == ULONG_MAX) || > ((kexec_segment_size >> PAGE_SHIFT) > totalram_pages() / 2)) { > pr_err("Binary measurement list too large.\n"); > return; > } > > - ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer, > - kexec_segment_size); Removing the call to ima_dump_measurement_list here is not bisect safe. > - if (!kexec_buffer) { > - pr_err("Not enough memory for the kexec measurement buffer.\n"); > + ret = ima_allocate_buf_at_kexec_load(); > + if (ret < 0) > return; > - } > > kbuf.buffer = kexec_buffer; > kbuf.bufsz = kexec_buffer_size;
Adding Eric to cc. On 7/7/23 06:01, Mimi Zohar wrote: > Hi Tushar, > > The function to "ima: allocate buffer at kexec load to hold ima > measurements" already exists. Please update the Subject line to > indicate increasing the IMA kexec buffer size. > > On Mon, 2023-07-03 at 14:57 -0700, Tushar Sugandhi wrote: >> The IMA subsystem needs a dedicated mechanism to reserve extra memory for >> measurements added between the kexec 'load' and kexec 'execute'. > What is a "dedicated mechanism?". Either start the sentence with > "reserve ..." or completely remove it. > Will do. >> Update ima_add_kexec_buffer to allocate a buffer of a sufficient size >> taking ima binary runtime measurements size, size of ima_kexec_hdr, and >> IMA_KEXEC_EXTRA_SIZE into account. Adjust the kexec_segment_size to align >> to the PAGE_SIZE. Call ima_allocate_buf_at_kexec_load() to allocate the >> buffer. > The size of the ima_kexec_hdr kind of gets lost in the amount of > additional memory being allocated, but sure it's a nice clean up. Thanks. :) >> This patch assumes the extra space defined (IMA_KEXEC_EXTRA_SIZE) is >> sufficient to handle the additional measurements. This should be as per >> the system requirements and based on the number of additional measurements >> expected during the window from kexec 'load' to kexec 'execute'. > Should the extra amount of memory be hard coded? > You are right. As you suggested below, defining the extra amount in Kconfig is a cleaner approach. >> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com> >> --- >> security/integrity/ima/ima.h | 2 ++ >> security/integrity/ima/ima_kexec.c | 21 ++++++++++----------- >> 2 files changed, 12 insertions(+), 11 deletions(-) >> >> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h >> index c29db699c996..2ffda9449b9b 100644 >> --- a/security/integrity/ima/ima.h >> +++ b/security/integrity/ima/ima.h >> @@ -43,6 +43,8 @@ enum tpm_pcrs { TPM_PCR0 = 0, TPM_PCR8 = 8, TPM_PCR10 = 10 }; >> >> #define NR_BANKS(chip) ((chip != NULL) ? chip->nr_allocated_banks : 0) >> >> +#define IMA_KEXEC_EXTRA_SIZE (16 * PAGE_SIZE) >> > Not all IMA policies require extra memory. Define and use a new IMA > Kconfig to set the amount of extra memory. Sure. Will do. >> /* current content of the policy */ >> extern int ima_policy_flag; >> >> diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c >> index 858b67689701..7deb8df31485 100644 >> --- a/security/integrity/ima/ima_kexec.c >> +++ b/security/integrity/ima/ima_kexec.c >> @@ -188,31 +188,30 @@ void ima_add_kexec_buffer(struct kimage *image) >> /* use more understandable variable names than defined in kbuf */ >> void *kexec_buffer = NULL; >> size_t kexec_buffer_size; >> - size_t kexec_segment_size; >> int ret; >> >> /* >> - * Reserve an extra half page of memory for additional measurements >> - * added during the kexec load. >> + * Reserve extra memory for measurements added in the window from >> + * kexec 'load' to kexec 'execute'. >> */ >> - binary_runtime_size = ima_get_binary_runtime_size(); >> + binary_runtime_size = ima_get_binary_runtime_size() + >> + sizeof(struct ima_kexec_hdr) + >> + IMA_KEXEC_EXTRA_SIZE; >> + >> if (binary_runtime_size >= ULONG_MAX - PAGE_SIZE) >> kexec_segment_size = ULONG_MAX; >> else >> - kexec_segment_size = ALIGN(ima_get_binary_runtime_size() + >> - PAGE_SIZE / 2, PAGE_SIZE); >> + kexec_segment_size = ALIGN(binary_runtime_size, PAGE_SIZE); >> + >> if ((kexec_segment_size == ULONG_MAX) || >> ((kexec_segment_size >> PAGE_SHIFT) > totalram_pages() / 2)) { >> pr_err("Binary measurement list too large.\n"); >> return; >> } >> >> - ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer, >> - kexec_segment_size); > Removing the call to ima_dump_measurement_list here is not bisect safe. Agreed. Will take care of this based on if we end up using just ima_dump_measurement_list(), or combination of ima_allocate_buf_at_kexec_load() and ima_populate_buf_at_kexec_execute(). ~Tushar >> - if (!kexec_buffer) { >> - pr_err("Not enough memory for the kexec measurement buffer.\n"); >> + ret = ima_allocate_buf_at_kexec_load(); >> + if (ret < 0) >> return; >> - } >> >> kbuf.buffer = kexec_buffer; >> kbuf.bufsz = kexec_buffer_size;
On 7/3/23 17:57, Tushar Sugandhi wrote: > The IMA subsystem needs a dedicated mechanism to reserve extra memory for > measurements added between the kexec 'load' and kexec 'execute'. > > Update ima_add_kexec_buffer to allocate a buffer of a sufficient size > taking ima binary runtime measurements size, size of ima_kexec_hdr, and > IMA_KEXEC_EXTRA_SIZE into account. Adjust the kexec_segment_size to align > to the PAGE_SIZE. Call ima_allocate_buf_at_kexec_load() to allocate the > buffer. > > This patch assumes the extra space defined (IMA_KEXEC_EXTRA_SIZE) is > sufficient to handle the additional measurements. This should be as per > the system requirements and based on the number of additional measurements > expected during the window from kexec 'load' to kexec 'execute'. This could be the most problematic part if the 'execute' happens much later than the 'load' with lots of measurement activity in between. I am wondering whether not doing anything at 'load' time and doing the whole work at 'execute' time wouldn't be the right thing to do ? Otherwise, if we wanted the work to be split as you suggest, could you - krealloc the src_pages (now in kimage_map_segment) to add space for a few more pages needed for the additional measurements - add those few more pages to src_pages - vunmap the previous mapping - vmap the extended src_pages array - update ima_kexec_file.buf with the diff between the new and old vmap'ed addresses - append to the existing log This presumably would help resolve this potential issue. The src_pages is currently not kfree'd -- may be a memory leak. Regards, Stefan > > Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com> > --- > security/integrity/ima/ima.h | 2 ++ > security/integrity/ima/ima_kexec.c | 21 ++++++++++----------- > 2 files changed, 12 insertions(+), 11 deletions(-) > > diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h > index c29db699c996..2ffda9449b9b 100644 > --- a/security/integrity/ima/ima.h > +++ b/security/integrity/ima/ima.h > @@ -43,6 +43,8 @@ enum tpm_pcrs { TPM_PCR0 = 0, TPM_PCR8 = 8, TPM_PCR10 = 10 }; > > #define NR_BANKS(chip) ((chip != NULL) ? chip->nr_allocated_banks : 0) > > +#define IMA_KEXEC_EXTRA_SIZE (16 * PAGE_SIZE) > + > /* current content of the policy */ > extern int ima_policy_flag; > > diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c > index 858b67689701..7deb8df31485 100644 > --- a/security/integrity/ima/ima_kexec.c > +++ b/security/integrity/ima/ima_kexec.c > @@ -188,31 +188,30 @@ void ima_add_kexec_buffer(struct kimage *image) > /* use more understandable variable names than defined in kbuf */ > void *kexec_buffer = NULL; > size_t kexec_buffer_size; > - size_t kexec_segment_size; > int ret; > > /* > - * Reserve an extra half page of memory for additional measurements > - * added during the kexec load. > + * Reserve extra memory for measurements added in the window from > + * kexec 'load' to kexec 'execute'. > */ > - binary_runtime_size = ima_get_binary_runtime_size(); > + binary_runtime_size = ima_get_binary_runtime_size() + > + sizeof(struct ima_kexec_hdr) + > + IMA_KEXEC_EXTRA_SIZE; > + > if (binary_runtime_size >= ULONG_MAX - PAGE_SIZE) > kexec_segment_size = ULONG_MAX; > else > - kexec_segment_size = ALIGN(ima_get_binary_runtime_size() + > - PAGE_SIZE / 2, PAGE_SIZE); > + kexec_segment_size = ALIGN(binary_runtime_size, PAGE_SIZE); > + > if ((kexec_segment_size == ULONG_MAX) || > ((kexec_segment_size >> PAGE_SHIFT) > totalram_pages() / 2)) { > pr_err("Binary measurement list too large.\n"); > return; > } > > - ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer, > - kexec_segment_size); > - if (!kexec_buffer) { > - pr_err("Not enough memory for the kexec measurement buffer.\n"); > + ret = ima_allocate_buf_at_kexec_load(); > + if (ret < 0) > return; > - } > > kbuf.buffer = kexec_buffer; > kbuf.bufsz = kexec_buffer_size;
On 7/11/23 13:16, Stefan Berger wrote: > > > On 7/3/23 17:57, Tushar Sugandhi wrote: >> The IMA subsystem needs a dedicated mechanism to reserve extra memory >> for >> measurements added between the kexec 'load' and kexec 'execute'. >> >> Update ima_add_kexec_buffer to allocate a buffer of a sufficient size >> taking ima binary runtime measurements size, size of ima_kexec_hdr, and >> IMA_KEXEC_EXTRA_SIZE into account. Adjust the kexec_segment_size to >> align >> to the PAGE_SIZE. Call ima_allocate_buf_at_kexec_load() to allocate the >> buffer. >> >> This patch assumes the extra space defined (IMA_KEXEC_EXTRA_SIZE) is >> sufficient to handle the additional measurements. This should be as per >> the system requirements and based on the number of additional >> measurements >> expected during the window from kexec 'load' to kexec 'execute'. > > This could be the most problematic part if the 'execute' happens much > later > than the 'load' with lots of measurement activity in between. I am > wondering > whether not doing anything at 'load' time and doing the whole work at > 'execute' time Technically I don't want to do anything at kexec 'load' time. But as I said elsewhere in this series, I am under impression that segment allocation must happen at kexec 'load' time. But if that understanding is wrong - then we can move the entire logic to kexec 'execute' time. I am currently trying to validate if moving the logic to kexec 'execute' works. > wouldn't be the right thing to do ? > > Otherwise, if we wanted the work to be split as you suggest, could you > - krealloc the src_pages (now in kimage_map_segment) to add space for > a few more pages needed for the additional measurements > - add those few more pages to src_pages > - vunmap the previous mapping > - vmap the extended src_pages array > - update ima_kexec_file.buf with the diff between the new and old > vmap'ed addresses > - append to the existing log > > This presumably would help resolve this potential issue. Thanks for the detailed thoughts. I will investigate if this approach is needed, based on my comment above. If it is needed and feasible, I will incorporate it in the next iteration. Thanks again. ~Tushar > > The src_pages is currently not kfree'd -- may be a memory leak. > > Regards, > Stefan > >> >> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com> >> --- >> security/integrity/ima/ima.h | 2 ++ >> security/integrity/ima/ima_kexec.c | 21 ++++++++++----------- >> 2 files changed, 12 insertions(+), 11 deletions(-) >> >> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h >> index c29db699c996..2ffda9449b9b 100644 >> --- a/security/integrity/ima/ima.h >> +++ b/security/integrity/ima/ima.h >> @@ -43,6 +43,8 @@ enum tpm_pcrs { TPM_PCR0 = 0, TPM_PCR8 = 8, >> TPM_PCR10 = 10 }; >> #define NR_BANKS(chip) ((chip != NULL) ? chip->nr_allocated_banks >> : 0) >> +#define IMA_KEXEC_EXTRA_SIZE (16 * PAGE_SIZE) >> + >> /* current content of the policy */ >> extern int ima_policy_flag; >> diff --git a/security/integrity/ima/ima_kexec.c >> b/security/integrity/ima/ima_kexec.c >> index 858b67689701..7deb8df31485 100644 >> --- a/security/integrity/ima/ima_kexec.c >> +++ b/security/integrity/ima/ima_kexec.c >> @@ -188,31 +188,30 @@ void ima_add_kexec_buffer(struct kimage *image) >> /* use more understandable variable names than defined in kbuf */ >> void *kexec_buffer = NULL; >> size_t kexec_buffer_size; >> - size_t kexec_segment_size; >> int ret; >> /* >> - * Reserve an extra half page of memory for additional measurements >> - * added during the kexec load. >> + * Reserve extra memory for measurements added in the window from >> + * kexec 'load' to kexec 'execute'. >> */ >> - binary_runtime_size = ima_get_binary_runtime_size(); >> + binary_runtime_size = ima_get_binary_runtime_size() + >> + sizeof(struct ima_kexec_hdr) + >> + IMA_KEXEC_EXTRA_SIZE; >> + >> if (binary_runtime_size >= ULONG_MAX - PAGE_SIZE) >> kexec_segment_size = ULONG_MAX; >> else >> - kexec_segment_size = ALIGN(ima_get_binary_runtime_size() + >> - PAGE_SIZE / 2, PAGE_SIZE); >> + kexec_segment_size = ALIGN(binary_runtime_size, PAGE_SIZE); >> + >> if ((kexec_segment_size == ULONG_MAX) || >> ((kexec_segment_size >> PAGE_SHIFT) > totalram_pages() / 2)) { >> pr_err("Binary measurement list too large.\n"); >> return; >> } >> - ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer, >> - kexec_segment_size); >> - if (!kexec_buffer) { >> - pr_err("Not enough memory for the kexec measurement >> buffer.\n"); >> + ret = ima_allocate_buf_at_kexec_load(); >> + if (ret < 0) >> return; >> - } >> kbuf.buffer = kexec_buffer; >> kbuf.bufsz = kexec_buffer_size;
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h index c29db699c996..2ffda9449b9b 100644 --- a/security/integrity/ima/ima.h +++ b/security/integrity/ima/ima.h @@ -43,6 +43,8 @@ enum tpm_pcrs { TPM_PCR0 = 0, TPM_PCR8 = 8, TPM_PCR10 = 10 }; #define NR_BANKS(chip) ((chip != NULL) ? chip->nr_allocated_banks : 0) +#define IMA_KEXEC_EXTRA_SIZE (16 * PAGE_SIZE) + /* current content of the policy */ extern int ima_policy_flag; diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c index 858b67689701..7deb8df31485 100644 --- a/security/integrity/ima/ima_kexec.c +++ b/security/integrity/ima/ima_kexec.c @@ -188,31 +188,30 @@ void ima_add_kexec_buffer(struct kimage *image) /* use more understandable variable names than defined in kbuf */ void *kexec_buffer = NULL; size_t kexec_buffer_size; - size_t kexec_segment_size; int ret; /* - * Reserve an extra half page of memory for additional measurements - * added during the kexec load. + * Reserve extra memory for measurements added in the window from + * kexec 'load' to kexec 'execute'. */ - binary_runtime_size = ima_get_binary_runtime_size(); + binary_runtime_size = ima_get_binary_runtime_size() + + sizeof(struct ima_kexec_hdr) + + IMA_KEXEC_EXTRA_SIZE; + if (binary_runtime_size >= ULONG_MAX - PAGE_SIZE) kexec_segment_size = ULONG_MAX; else - kexec_segment_size = ALIGN(ima_get_binary_runtime_size() + - PAGE_SIZE / 2, PAGE_SIZE); + kexec_segment_size = ALIGN(binary_runtime_size, PAGE_SIZE); + if ((kexec_segment_size == ULONG_MAX) || ((kexec_segment_size >> PAGE_SHIFT) > totalram_pages() / 2)) { pr_err("Binary measurement list too large.\n"); return; } - ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer, - kexec_segment_size); - if (!kexec_buffer) { - pr_err("Not enough memory for the kexec measurement buffer.\n"); + ret = ima_allocate_buf_at_kexec_load(); + if (ret < 0) return; - } kbuf.buffer = kexec_buffer; kbuf.bufsz = kexec_buffer_size;
The IMA subsystem needs a dedicated mechanism to reserve extra memory for measurements added between the kexec 'load' and kexec 'execute'. Update ima_add_kexec_buffer to allocate a buffer of a sufficient size taking ima binary runtime measurements size, size of ima_kexec_hdr, and IMA_KEXEC_EXTRA_SIZE into account. Adjust the kexec_segment_size to align to the PAGE_SIZE. Call ima_allocate_buf_at_kexec_load() to allocate the buffer. This patch assumes the extra space defined (IMA_KEXEC_EXTRA_SIZE) is sufficient to handle the additional measurements. This should be as per the system requirements and based on the number of additional measurements expected during the window from kexec 'load' to kexec 'execute'. Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com> --- security/integrity/ima/ima.h | 2 ++ security/integrity/ima/ima_kexec.c | 21 ++++++++++----------- 2 files changed, 12 insertions(+), 11 deletions(-)