Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 34543c03 authored by Prashant Malani's avatar Prashant Malani
Browse files

fs_mgr: Add support for at-boot verification 

Running dm-verity on heavily accessed partitions leads to performance
slowdowns, especially on low-RAM and slow-CPU devices.

This patch introduces a flag to allow an entire verified partition to be
read once at boot, to check for corruptions. If the reads are
successful, we can mount the partition as raw & read-only, and if not,
we can revert to mounting it as a verity partition, just like before.

Usage of this flag will entail a slowdown of time-to-boot, but should
lead to improvements in runtime performance.

Bug: 32433608
Change-Id: I97717683a00ad6fa347e63b72b1a9bf1d2946315
parent 6f831490

fs_mgr/fs_mgr_fstab.c

+1 −0
Original line number Diff line number Diff line
@@ -72,6 +72,7 @@ static struct flag_list fs_mgr_flags[] = { 
    { "recoveryonly",MF_RECOVERYONLY },

    { "swapprio=",   MF_SWAPPRIO },

    { "zramsize=",   MF_ZRAMSIZE },

    { "verifyatboot", MF_VERIFYATBOOT },

    { "verify",      MF_VERIFY },

    { "noemulatedsd", MF_NOEMULATEDSD },

    { "notrim",       MF_NOTRIM },

fs_mgr/fs_mgr_priv.h

+1 −0
Original line number Diff line number Diff line
@@ -85,6 +85,7 @@ __BEGIN_DECLS 
#define MF_FORCEFDEORFBE 0x10000

#define MF_LATEMOUNT    0x20000

#define MF_NOFAIL       0x40000

#define MF_VERIFYATBOOT 0x80000



#define DM_BUF_SIZE 4096

fs_mgr/fs_mgr_verity.cpp

+57 −3
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ 


#include <android-base/file.h>

#include <android-base/strings.h>

#include <android-base/unique_fd.h>

#include <cutils/properties.h>

#include <logwrap/logwrap.h>
@@ -72,6 +73,8 @@ 
#define VERITY_KMSG_RESTART "dm-verity device corrupted"

#define VERITY_KMSG_BUFSIZE 1024



#define READ_BUF_SIZE 4096



#define __STRINGIFY(x) #x

#define STRINGIFY(x) __STRINGIFY(x)
@@ -213,6 +216,16 @@ static int create_verity_device(struct dm_ioctl *io, char *name, int fd) 
    return 0;

}



static int destroy_verity_device(struct dm_ioctl *io, char *name, int fd)

{

    verity_ioctl_init(io, name, 0);

    if (ioctl(fd, DM_DEV_REMOVE, io)) {

        ERROR("Error removing device mapping (%s)", strerror(errno));

        return -1;

    }

    return 0;

}



static int get_verity_device_name(struct dm_ioctl *io, char *name, int fd, char **dev_name)

{

    verity_ioctl_init(io, name, 0);
@@ -614,6 +627,30 @@ out: 
    return rc;

}



static int read_partition(const char *path, uint64_t size)

{

    char buf[READ_BUF_SIZE];

    ssize_t size_read;

    android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(path, O_RDONLY | O_CLOEXEC)));



    if (fd == -1) {

        ERROR("Failed to open %s: %s\n", path, strerror(errno));

        return -errno;

    }



    while (size) {

        size_read = TEMP_FAILURE_RETRY(read(fd, buf, READ_BUF_SIZE));

        if (size_read == -1) {

            ERROR("Error in reading partition %s: %s\n", path,

                  strerror(errno));

            return -errno;

        }

        size -= size_read;

    }



    return 0;

}



static int compare_last_signature(struct fstab_rec *fstab, int *match)

{

    char tag[METADATA_TAG_MAX_LENGTH + 1];
@@ -908,6 +945,7 @@ int fs_mgr_setup_verity(struct fstab_rec *fstab) 
    struct fec_handle *f = NULL;

    struct fec_verity_metadata verity;

    struct verity_table_params params = { .table = NULL };

    bool verified_at_boot = false;



    alignas(dm_ioctl) char buffer[DM_BUF_SIZE];

    struct dm_ioctl *io = (struct dm_ioctl *) buffer;
@@ -1045,10 +1083,26 @@ loaded: 
    // mark the underlying block device as read-only

    fs_mgr_set_blk_ro(fstab->blk_device);



    // Verify the entire partition in one go

    // If there is an error, allow it to mount as a normal verity partition.

    if (fstab->fs_mgr_flags & MF_VERIFYATBOOT) {

        INFO("Verifying partition %s at boot\n", fstab->blk_device);

        int err = read_partition(verity_blk_name, verity.data_size);

        if (!err) {

            INFO("Verified verity partition %s at boot\n", fstab->blk_device);

            verified_at_boot = true;

        }

    }



    // assign the new verity block device as the block device

    if (!verified_at_boot) {

        free(fstab->blk_device);

        fstab->blk_device = verity_blk_name;

        verity_blk_name = 0;

    } else if (destroy_verity_device(io, mount_point, fd) < 0) {

        ERROR("Failed to remove verity device %s\n", mount_point);

        goto out;

    }



    // make sure we've set everything up properly

    if (test_access(fstab->blk_device) < 0) {