On 03/19/25 at 12:27pm, Mimi Zohar wrote: > On Wed, 2025-03-19 at 16:09 +0800, Baoquan He wrote: > > On 03/17/25 at 06:04pm, 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(). > > > - Make necessary changes to the function ima_add_kexec_buffer() to call > > > the above two functions. > > > > We may not need above details about code change because it's not so > > difficult to get them from patch. > > Agreed. The changes don't even reflect the current patch. Please remove the > entire section. > > > > > > > > > Signed-off-by: Tushar Sugandhi <[email protected]> > > > Signed-off-by: steven chen <[email protected]> > > > --- > > > security/integrity/ima/ima_kexec.c | 67 +++++++++++++++++++++++++----- > > > 1 file changed, 56 insertions(+), 11 deletions(-) > > > > > > diff --git a/security/integrity/ima/ima_kexec.c > > > b/security/integrity/ima/ima_kexec.c > > > index 8567619889d1..45170e283272 100644 > > > --- a/security/integrity/ima/ima_kexec.c > > > +++ b/security/integrity/ima/ima_kexec.c > > > @@ -15,6 +15,48 @@ > > > #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; > > The call to ima_reset_kexec_file() in ima_add_kexec_buffer() resets > ima_kexec_file.buf() hiding the fact that the above test always fails and > falls > through. As a result, 'buf' is always being re-allocated. > > > > + > > > + 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; > > > +} > > > + > > > /* > > > * Copy the measurement list to the allocated memory > > > * compare the size of IMA measurement list with the size of the > > > allocated memory > > > @@ -26,23 +68,16 @@ > > > static int ima_dump_measurement_list(unsigned long *buffer_size, void > > > **buffer, > > > unsigned long segment_size) > > > { > > > - struct seq_file ima_kexec_file; > > > struct ima_queue_entry *qe; > > > struct ima_kexec_hdr khdr; > > > int ret = 0; > > > > > > /* segment size can't change between kexec load and execute */ > > > - ima_kexec_file.buf = vmalloc(segment_size); > > > if (!ima_kexec_file.buf) { > > > - ret = -ENOMEM; > > > - goto out; > > > + pr_err("Kexec file buf not allocated\n"); > > > + return -EINVAL; > > > } > > > > > > - ima_kexec_file.file = NULL; > > > - ima_kexec_file.size = segment_size; > > > - ima_kexec_file.read_pos = 0; > > > - ima_kexec_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 */ > > > @@ -79,8 +114,6 @@ static int ima_dump_measurement_list(unsigned long > > > *buffer_size, void **buffer, > > > *buffer_size = ima_kexec_file.count; > > > *buffer = ima_kexec_file.buf; > > > out: > > > - if (ret == -EINVAL) > > > - vfree(ima_kexec_file.buf); > > > return ret; > > > } > > > > > > @@ -119,6 +152,12 @@ void ima_add_kexec_buffer(struct kimage *image) > > > return; > > > } > > > > > > + ret = ima_alloc_kexec_file_buf(kexec_segment_size); > > > + if (ret < 0) { > > > + pr_err("Not enough memory for the kexec measurement buffer.\n"); > > > + return; > > > + } > > > + > > > ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer, > > > kexec_segment_size); > > > if (!kexec_buffer) { > > > @@ -140,6 +179,12 @@ 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); > > > > I can't see why we need call ima_reset_kexec_file() here. If we need > > reuse the buffer, we will reset the needed fields at the end of > > ima_alloc_kexec_file_buf(). Not sure if I miss anything. > > Without ima_reset_kexec_file(), calling 'kexec load' consecutively without > "kexec -s -e" in between fails. > > # kexec -s -l /boot/vmlinuz-`uname -r` --initrd=/boot/initramfs-`uname > -r`.img --reuse-cmdline > # kexec -s -l /boot/vmlinuz-`uname -r` --initrd=/boot/initramfs-`uname > -r`.img --reuse-cmdline > Killed > > As mentioned above, the call to ima_reset_kexec_file() resets > ima_kexec_file.buf, so the segment size test always fails and the memory is > being allocated.
Indeed, I didn't realize this.
