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

Commit 170c1332 authored by Keith Mok's avatar Keith Mok Committed by Automerger Merge Worker
Browse files

Add seal if ashmem-dev is backed by memfd am: 61a28977 am: 7878e7c9 am: fb73f178 

Original change: https://googleplex-android-review.googlesource.com/c/platform/system/core/+/24776869



Change-Id: Ieebb2b1f87aba8c1427cc4dfb112fe9f40e1956d
Signed-off-by: default avatarAutomerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
parents 783a714b fb73f178

libcutils/ashmem-dev.cpp

+25 −4
Original line number Diff line number Diff line
@@ -349,6 +349,12 @@ static int memfd_create_region(const char* name, size_t size) { 
        return -1;

    }



    // forbid size changes to match ashmem behaviour

    if (fcntl(fd, F_ADD_SEALS, F_SEAL_GROW | F_SEAL_SHRINK) == -1) {

        ALOGE("memfd_create(%s, %zd) F_ADD_SEALS failed: %m", name, size);

        return -1;

    }



    if (debug_log) {

        ALOGE("memfd_create(%s, %zd) success. fd=%d\n", name, size, fd.get());

    }
@@ -400,14 +406,29 @@ error: 
}



static int memfd_set_prot_region(int fd, int prot) {

    /* Only proceed if an fd needs to be write-protected */

    int seals = fcntl(fd, F_GET_SEALS);

    if (seals == -1) {

        ALOGE("memfd_set_prot_region(%d, %d): F_GET_SEALS failed: %s\n", fd, prot, strerror(errno));

        return -1;

    }



    if (prot & PROT_WRITE) {

        /* Now we want the buffer to be read-write, let's check if the buffer

         * has been previously marked as read-only before, if so return error

         */

        if (seals & F_SEAL_FUTURE_WRITE) {

            ALOGE("memfd_set_prot_region(%d, %d): region is write protected\n", fd, prot);

            errno = EINVAL;  // inline with ashmem error code, if already in

                             // read-only mode

            return -1;

        }

        return 0;

    }



    if (fcntl(fd, F_ADD_SEALS, F_SEAL_FUTURE_WRITE) == -1) {

        ALOGE("memfd_set_prot_region(%d, %d): F_SEAL_FUTURE_WRITE seal failed: %s\n", fd, prot,

              strerror(errno));

    /* We would only allow read-only for any future file operations */

    if (fcntl(fd, F_ADD_SEALS, F_SEAL_FUTURE_WRITE | F_SEAL_SEAL) == -1) {

        ALOGE("memfd_set_prot_region(%d, %d): F_SEAL_FUTURE_WRITE | F_SEAL_SEAL seal failed: %s\n",

              fd, prot, strerror(errno));

        return -1;

    }