Verified Commit 68fa711b authored by Marc Vef's avatar Marc Vef
Browse files

Temporary fix for ADA-FS and kernel file descriptor value clashes.

parent 6422d40a

ifs/src/preload/intcp_functions.cpp

+2 −0
Original line number Diff line number Diff line
@@ -332,6 +332,7 @@ int ftruncate(int fd, off_t length) __THROW { 
int dup(int oldfd) __THROW {

    init_passthrough_if_needed();

    if (ld_is_aux_loaded() && file_map.exist(oldfd)) {

        ld_logger->trace("{}() called with oldfd {}", __func__, oldfd);

        return adafs_dup(oldfd);

    }

    return (reinterpret_cast<decltype(&dup)>(libc_dup))(oldfd);
@@ -340,6 +341,7 @@ int dup(int oldfd) __THROW { 
int dup2(int oldfd, int newfd) __THROW {

    init_passthrough_if_needed();

    if (ld_is_aux_loaded() && file_map.exist(oldfd)) {

        ld_logger->trace("{}() called with oldfd {} newfd {}", __func__, oldfd, newfd);

        return adafs_dup2(oldfd, newfd);

    }

    return (reinterpret_cast<decltype(&dup2)>(libc_dup2))(oldfd, newfd);

ifs/src/preload/preload_util.cpp

+11 −3
Original line number Diff line number Diff line
@@ -10,7 +10,15 @@ using namespace std; 


static const std::string dentry_val_delim = ","s;



static int fd_idx = 3;

/*

 * TODO: Setting our file descriptor index to a specific value is dangerous because we might clash with the kernel.

 * E.g., if we would passthrough and not intercept and the kernel assigns a file descriptor but we will later use

 * the same fd value, we will intercept calls that were supposed to be going to the kernel. This works the other way around too.

 * To mitigate this issue, we set the initial fd number to a high value. We "hope" that we do not clash but this is no permanent solution.

 * Note: This solution will probably work well already for many cases because kernel fd values are reused, unlike to ours.

 * The only case where we will clash with the kernel is, if one process has more than 100000 files open at the same time.

 */

static int fd_idx = 100000;

static mutex fd_idx_mutex;

std::atomic<bool> fd_validation_needed(false);
@@ -22,13 +30,13 @@ int generate_fd_idx() { 
    // We need a mutex here for thread safety

    std::lock_guard<std::mutex> inode_lock(fd_idx_mutex);

    if (fd_idx == std::numeric_limits<int>::max()) {

        ld_logger->info("{}() File descriptor index exceeded ints max value. Setting it back to 3", __func__);

        ld_logger->info("{}() File descriptor index exceeded ints max value. Setting it back to 100000", __func__);

        /*

         * Setting fd_idx back to 3 could have the effect that fd are given twice for different path.

         * This must not happen. Instead a flag is set which tells can tell the OpenFileMap that it should check

         * if this fd is really safe to use.

         */

        fd_idx = 3;

        fd_idx = 100000;

        fd_validation_needed = true;

    }

    return fd_idx++;