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Add seal if ashmem-dev is backed by memfd am: 61a2897733 am: 7878e7c9b7 am: fb73f1789e am: 170c133259 am: 72add75484

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

Change-Id: Ibc20777c221527cd61f0c005c5095c42c1ab5a40
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
This commit is contained in:
Keith Mok 2023-10-27 23:42:36 +00:00 committed by Automerger Merge Worker
commit 87675df8a6
1 changed files with 25 additions and 4 deletions
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29
libcutils/ashmem-dev.cpp
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@ -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;
}