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Commit c811d139 authored by Yi-Yo Chiang's avatar Yi-Yo Chiang
Browse files

Add ParseFstabFromString(), remove ReadFstabFromFp() 

ReadFstabFromFp() have two callers right now, ReadFstabFromFile() and
ReadFstabFromDt(). ReadFstabFromFile() opens a FILE* and pass it to
ReadFstabFromFp(), and ReadFstabFromDt() wraps a std::string::c_str()
buffer in a FILE* adaptor with fmemopen().

There's no need for such adaptor, just change ReadFstabFromFp() to
accept std::string and we're good.

Bug: 204056804
Test: atest CtsFsMgrTestCases
Test: m libfstab_fuzzer
Change-Id: I71190c7356a354aa06d1be3fdc4ca76611b3896d
parent 3c1b581f

fs_mgr/fs_mgr_fstab.cpp

+21 −42
Original line number Diff line number Diff line
@@ -525,34 +525,23 @@ bool EraseFstabEntry(Fstab* fstab, const std::string& mount_point) { 


}  // namespace



bool ReadFstabFromFp(FILE* fstab_file, bool proc_mounts, Fstab* fstab_out) {

bool ParseFstabFromString(const std::string& fstab_str, bool proc_mounts, Fstab* fstab_out) {

    const int expected_fields = proc_mounts ? 4 : 5;

    ssize_t len;

    size_t alloc_len = 0;

    char *line = NULL;

    char* p;



    Fstab fstab;



    while ((len = getline(&line, &alloc_len, fstab_file)) != -1) {

        /* if the last character is a newline, shorten the string by 1 byte */

        if (line[len - 1] == '\n') {

            line[len - 1] = '\0';

        }

    for (const auto& line : android::base::Split(fstab_str, "\n")) {

        auto fields = android::base::Tokenize(line, " \t");



        /* Skip any leading whitespace */

        p = line;

        while (isspace(*p)) {

            p++;

        }

        /* ignore comments or empty lines */

        if (*p == '#' || *p == '\0')

        // Ignore empty lines and comments.

        if (fields.empty() || android::base::StartsWith(fields.front(), '#')) {

            continue;

        }



        auto fields = android::base::Tokenize(line, " \t");

        if (fields.size() < expected_fields) {

            LERROR << "Error parsing fstab: expected " << expected_fields << " fields, got "

                   << fields.size();

            goto err;

            return false;

        }



        FstabEntry entry;
@@ -566,7 +555,7 @@ bool ReadFstabFromFp(FILE* fstab_file, bool proc_mounts, Fstab* fstab_out) { 
        // For /proc/mounts, ignore everything after mnt_freq and mnt_passno

        if (!proc_mounts && !ParseFsMgrFlags(std::move(*it++), &entry)) {

            LERROR << "Error parsing fs_mgr_flags";

            goto err;

            return false;

        }



        if (entry.fs_mgr_flags.logical) {
@@ -578,21 +567,17 @@ bool ReadFstabFromFp(FILE* fstab_file, bool proc_mounts, Fstab* fstab_out) { 


    if (fstab.empty()) {

        LERROR << "No entries found in fstab";

        goto err;

        return false;

    }



    /* If an A/B partition, modify block device to be the real block device */

    if (!fs_mgr_update_for_slotselect(&fstab)) {

        LERROR << "Error updating for slotselect";

        goto err;

        return false;

    }

    free(line);



    *fstab_out = std::move(fstab);

    return true;



err:

    free(line);

    return false;

}



void TransformFstabForDsu(Fstab* fstab, const std::string& dsu_slot,
@@ -691,16 +676,18 @@ void EnableMandatoryFlags(Fstab* fstab) { 
}



bool ReadFstabFromFile(const std::string& path, Fstab* fstab_out) {

    auto fstab_file = std::unique_ptr<FILE, decltype(&fclose)>{fopen(path.c_str(), "re"), fclose};

    if (!fstab_file) {

        PERROR << __FUNCTION__ << "(): cannot open file: '" << path << "'";

    const bool is_proc_mounts = (path == "/proc/mounts");

    // /proc/mounts could be a symlink to /proc/self/mounts.

    const bool follow_symlinks = is_proc_mounts;



    std::string fstab_str;

    if (!android::base::ReadFileToString(path, &fstab_str, follow_symlinks)) {

        PERROR << __FUNCTION__ << "(): failed to read file: '" << path << "'";

        return false;

    }



    bool is_proc_mounts = path == "/proc/mounts";



    Fstab fstab;

    if (!ReadFstabFromFp(fstab_file.get(), is_proc_mounts, &fstab)) {

    if (!ParseFstabFromString(fstab_str, is_proc_mounts, &fstab)) {

        LERROR << __FUNCTION__ << "(): failed to load fstab from : '" << path << "'";

        return false;

    }
@@ -747,15 +734,7 @@ bool ReadFstabFromDt(Fstab* fstab, bool verbose) { 
        return false;

    }



    std::unique_ptr<FILE, decltype(&fclose)> fstab_file(

        fmemopen(static_cast<void*>(const_cast<char*>(fstab_buf.c_str())),

                 fstab_buf.length(), "r"), fclose);

    if (!fstab_file) {

        if (verbose) PERROR << __FUNCTION__ << "(): failed to create a file stream for fstab dt";

        return false;

    }



    if (!ReadFstabFromFp(fstab_file.get(), false, fstab)) {

    if (!ParseFstabFromString(fstab_buf, /* proc_mounts = */ false, fstab)) {

        if (verbose) {

            LERROR << __FUNCTION__ << "(): failed to load fstab from kernel:" << std::endl

                   << fstab_buf;

fs_mgr/fuzz/fs_mgr_fstab_fuzzer.cpp

+2 −6
Original line number Diff line number Diff line
@@ -19,12 +19,8 @@ 
#include <fstab/fstab.h>



extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {

    std::unique_ptr<FILE, decltype(&fclose)> fstab_file(

            fmemopen(static_cast<void*>(const_cast<uint8_t*>(data)), size, "r"), fclose);

    if (fstab_file == nullptr) {

        return 0;

    }

    std::string make_fstab_str(reinterpret_cast<const char*>(data), size);

    android::fs_mgr::Fstab fstab;

    android::fs_mgr::ReadFstabFromFp(fstab_file.get(), /* proc_mounts= */ false, &fstab);

    android::fs_mgr::ParseFstabFromString(make_fstab_str, /* proc_mounts = */ false, &fstab);

    return 0;

}

fs_mgr/include_fstab/fstab/fstab.h

+2 −2
Original line number Diff line number Diff line
@@ -94,8 +94,8 @@ struct FstabEntry { 
// Unless explicitly requested, a lookup on mount point should always return the 1st one.

using Fstab = std::vector<FstabEntry>;



// Exported for testability. Regular users should use ReadFstabFromfile().

bool ReadFstabFromFp(FILE* fstab_file, bool proc_mounts, Fstab* fstab_out);

// Exported for testability. Regular users should use ReadFstabFromFile().

bool ParseFstabFromString(const std::string& fstab_str, bool proc_mounts, Fstab* fstab_out);



bool ReadFstabFromFile(const std::string& path, Fstab* fstab);

bool ReadFstabFromDt(Fstab* fstab, bool verbose = true);