On Tue, 2025-02-18 at 14:54 -0800, steven chen wrote: > Carrying the IMA measurement list across kexec requires allocating a > buffer and copying the measurement records. Separate allocating the > buffer and copying the measurement records into separate functions in > order to allocate the buffer at kexec 'load' and copy the measurements > at kexec 'execute'. > > This patch includes the following changes: > - Refactor ima_dump_measurement_list() to move the memory allocation > to a separate function ima_alloc_kexec_file_buf() which allocates > buffer of size 'kexec_segment_size' at kexec 'load'. > - Make the local variable ima_kexec_file in ima_dump_measurement_list() > a local static to the file, so that it can be accessed from > ima_alloc_kexec_file_buf(). Compare actual memory required to ensure > there is enough memory for the entire measurement record. > - Copy as many measurement events as possible. > - Make necessary changes to the function ima_add_kexec_buffer() to call > the above two functions. > - Compared the memory size allocated with memory size of the entire > measurement record. If there is not enough memory, it will copy as many > IMA measurement records as possible, and this situation will result > in a failure of remote attestation. > > Author: Tushar Sugandhi <tusha...@linux.microsoft.com>
Steven, thank you again for picking up this patch set. As previously explained, there is no tag named "Author" in https://www.kernel.org/doc/Documentation/process/submitting-patches.rst. To give credit to the original author use "Co-developed-by". The "Co-developed-by:" tag is immediately followed by the original author's "Signed-off-by:" tag. Please refer to the document for an example. > Suggested-by: Mimi Zohar <zo...@linux.ibm.com> <--- "Co-developed-by:" would go here. > Signed-off-by: Tushar Sugandhi <tusha...@linux.microsoft.com> > Signed-off-by: steven chen <chen...@linux.microsoft.com> > --- > security/integrity/ima/ima.h | 1 + > security/integrity/ima/ima_kexec.c | 102 +++++++++++++++++++++-------- > security/integrity/ima/ima_queue.c | 4 +- > 3 files changed, 77 insertions(+), 30 deletions(-) > > diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h > index 24d09ea91b87..4428fcf42167 100644 > --- a/security/integrity/ima/ima.h > +++ b/security/integrity/ima/ima.h > @@ -274,6 +274,7 @@ bool ima_template_has_modsig(const struct > ima_template_desc > *ima_template); > int ima_restore_measurement_entry(struct ima_template_entry *entry); > int ima_restore_measurement_list(loff_t bufsize, void *buf); > int ima_measurements_show(struct seq_file *m, void *v); > +int ima_get_binary_runtime_entry_size(struct ima_template_entry *entry); > unsigned long ima_get_binary_runtime_size(void); > int ima_init_template(void); > void ima_init_template_list(void); > diff --git a/security/integrity/ima/ima_kexec.c > b/security/integrity/ima/ima_kexec.c > index 9d45f4d26f73..89088f1fa989 100644 > --- a/security/integrity/ima/ima_kexec.c > +++ b/security/integrity/ima/ima_kexec.c > @@ -15,63 +15,97 @@ > #include "ima.h" > > #ifdef CONFIG_IMA_KEXEC > +static struct seq_file ima_kexec_file; > + > +static void ima_reset_kexec_file(struct seq_file *sf) > +{ > + sf->buf = NULL; > + sf->size = 0; > + sf->read_pos = 0; > + sf->count = 0; > +} > + > +static void ima_free_kexec_file_buf(struct seq_file *sf) > +{ > + vfree(sf->buf); > + ima_reset_kexec_file(sf); > +} > + > +static int ima_alloc_kexec_file_buf(size_t segment_size) > +{ > + /* > + * kexec 'load' may be called multiple times. > + * Free and realloc the buffer only if the segment_size is > + * changed from the previous kexec 'load' call. > + */ > + if (ima_kexec_file.buf && ima_kexec_file.size == segment_size) > + goto out; > + > + ima_free_kexec_file_buf(&ima_kexec_file); > + > + /* segment size can't change between kexec load and execute */ > + ima_kexec_file.buf = vmalloc(segment_size); > + if (!ima_kexec_file.buf) > + return -ENOMEM; > + > + ima_kexec_file.size = segment_size; > + > +out: > + ima_kexec_file.read_pos = 0; > + ima_kexec_file.count = sizeof(struct ima_kexec_hdr); /* reserved > space */ > + > + return 0; > +} > + <--- ima_dump_measurement_list() function comment goes here. > static int ima_dump_measurement_list(unsigned long *buffer_size, void > **buffer, > unsigned long segment_size) > { > struct ima_queue_entry *qe; > - struct seq_file file; > struct ima_kexec_hdr khdr; > int ret = 0; > + size_t entry_size = 0; > > - /* segment size can't change between kexec load and execute */ > - file.buf = vmalloc(segment_size); > - if (!file.buf) { > - ret = -ENOMEM; > - goto out; > + if (!ima_kexec_file.buf) { > + pr_err("Kexec file buf not allocated\n"); > + return -EINVAL; > } > > - file.file = NULL; > - file.size = segment_size; > - file.read_pos = 0; > - file.count = sizeof(khdr); /* reserved space */ > - > memset(&khdr, 0, sizeof(khdr)); > khdr.version = 1; > /* This is an append-only list, no need to hold the RCU read lock */ > + /* Copy as many IMA measurements list records as possible */ Having two consecutive comments like this looks weird. Please refer to section "8) Commenting" of https://www.kernel.org/doc/Documentation/process/coding-style.rst. The first comment is particular to list_for_each_entry_rcu() and should remain here. The latter comment is more generic and should be included as part of a function comment. > list_for_each_entry_rcu(qe, &ima_measurements, later, true) { > - if (file.count < file.size) { > + entry_size += ima_get_binary_runtime_entry_size(qe->entry); > + if (entry_size <= segment_size) { As much as possible splitting a function shouldn't change the existing code. It makes it harder to review. This sort of change should be a separate patch with the Subject topic line something like "ima: copy only complete measurement records across kexec". Making this change as the first patch in the patch set will also allow it to be backported. > khdr.count++; > - ima_measurements_show(&file, qe); > + ima_measurements_show(&ima_kexec_file, qe); > } else { > ret = -EINVAL; > + pr_err("IMA log file is too big for Kexec buf\n"); > break; We really DO want to "Copy as many IMA measurements list records as possible" as possible. However, the code doesn't match the comment, since the caller of ima_dump_measurement_list() treats -EINVAL as an error and bails. > } > } > > - if (ret < 0) > - goto out; > - > /* > * fill in reserved space with some buffer details > * (eg. version, buffer size, number of measurements) > */ > - khdr.buffer_size = file.count; > + khdr.buffer_size = ima_kexec_file.count; > if (ima_canonical_fmt) { > khdr.version = cpu_to_le16(khdr.version); > khdr.count = cpu_to_le64(khdr.count); > khdr.buffer_size = cpu_to_le64(khdr.buffer_size); > } > - memcpy(file.buf, &khdr, sizeof(khdr)); > + memcpy(ima_kexec_file.buf, &khdr, sizeof(khdr)); > > print_hex_dump_debug("ima dump: ", DUMP_PREFIX_NONE, 16, 1, > - file.buf, file.count < 100 ? file.count : 100, > + ima_kexec_file.buf, ima_kexec_file.count < 100 ? > + ima_kexec_file.count : 100, > true); > > - *buffer_size = file.count; > - *buffer = file.buf; > -out: > - if (ret == -EINVAL) > - vfree(file.buf); > + *buffer_size = ima_kexec_file.count; > + *buffer = ima_kexec_file.buf; > + > return ret; > } > > @@ -90,7 +124,7 @@ 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_buffer_size = 0; > size_t kexec_segment_size; > int ret; > > @@ -110,13 +144,19 @@ void ima_add_kexec_buffer(struct kimage *image) > return; > } > > - ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer, > - kexec_segment_size); > - if (!kexec_buffer) { > + ret = ima_alloc_kexec_file_buf(kexec_segment_size); > + if (ret < 0) { > pr_err("Not enough memory for the kexec measurement buffer.\n"); > return; > } > > + ret = ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer, > + kexec_segment_size); > + if (ret < 0) { > + pr_err("Failed to dump IMA measurements. Error:%d.\n", ret); > + return; > + } > + As mentioned above, we really do want to copy as many measurement records as possible across kexec. > kbuf.buffer = kexec_buffer; > kbuf.bufsz = kexec_buffer_size; > kbuf.memsz = kexec_segment_size; > @@ -131,6 +171,12 @@ void ima_add_kexec_buffer(struct kimage *image) > image->ima_buffer_size = kexec_segment_size; > image->ima_buffer = kexec_buffer; > > + /* > + * kexec owns kexec_buffer after kexec_add_buffer() is called > + * and it will vfree() that buffer. > + */ > + ima_reset_kexec_file(&ima_kexec_file); > + > kexec_dprintk("kexec measurement buffer for the loaded kernel at > 0x%lx.\n", > kbuf.mem); > } > diff --git a/security/integrity/ima/ima_queue.c > b/security/integrity/ima/ima_queue.c > index 83d53824aa98..3dfd178d4292 100644 > --- a/security/integrity/ima/ima_queue.c > +++ b/security/integrity/ima/ima_queue.c > @@ -78,7 +78,7 @@ static struct ima_queue_entry *ima_lookup_digest_entry(u8 > *digest_value, > * binary_runtime_measurement list entry, which contains a > * couple of variable length fields (e.g template name and data). > */ > -static int get_binary_runtime_size(struct ima_template_entry *entry) > +int ima_get_binary_runtime_entry_size(struct ima_template_entry *entry) > { > int size = 0; > > @@ -122,7 +122,7 @@ static int ima_add_digest_entry(struct ima_template_entry > *entry, > if (binary_runtime_size != ULONG_MAX) { > int size; > > - size = get_binary_runtime_size(entry); > + size = ima_get_binary_runtime_entry_size(entry); > binary_runtime_size = (binary_runtime_size < ULONG_MAX - size) ? > binary_runtime_size + size : ULONG_MAX; > } This change would be included in the new first patch named something like "ima: copy only complete measurement records across kexec". Thanks, Mimi
