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Commit 5792ce79 authored by David 'Digit' Turner's avatar David 'Digit' Turner Committed by Jean-Baptiste Queru
Browse files

run-as: use mmap to read package list file 

This patch uses mmap() to read /data/system/packages.list

This avoids depending on the size of a fixed static buffer
which may happen to be too short for systems with a lot of
packages installed.

Also avoids calling malloc() which we don't want to trust here
since run-as is a setuid program.

Change-Id: I1d640a08b5d73af2fc80546b01c8d970c7f6b514
parent de90da4d

run-as/package.c

+59 −32
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
#include <fcntl.h>

#include <unistd.h>

#include <sys/stat.h>

#include <sys/mman.h>

#include <private/android_filesystem_config.h>

#include "package.h"
@@ -43,9 +44,6 @@ 
/* The file containing the list of installed packages on the system */

#define PACKAGES_LIST_FILE  "/data/system/packages.list"



/* This should be large enough to hold the content of the package database file */

#define PACKAGES_LIST_BUFFER_SIZE  65536



/* Copy 'srclen' string bytes from 'src' into buffer 'dst' of size 'dstlen'

 * This function always zero-terminate the destination buffer unless

 * 'dstlen' is 0, even in case of overflow.
@@ -67,40 +65,63 @@ string_copy(char* dst, size_t dstlen, const char* src, size_t srclen) 
    *dst = '\0'; /* zero-terminate result */

}



/* Read up to 'buffsize' bytes into 'buff' from the file

 * named 'filename'. Return byte length on success, or -1

 * on error.

/* Open 'filename' and map it into our address-space.

 * Returns buffer address, or NULL on error

 * On exit, *filesize will be set to the file's size, or 0 on error

 */

static int

read_file(const char* filename, char* buff, size_t buffsize)

static void*

map_file(const char* filename, size_t* filesize)

{

    int  fd, len, old_errno;

    int  fd, ret, old_errno;

    struct stat  st;

    size_t  length = 0;

    void*   address = NULL;



    /* check the input buffer size */

    if (buffsize >= INT_MAX) {

        errno = EINVAL;

        return -1;

    }

    *filesize = 0;



    /* open the file for reading */

    do {

        fd = open(filename, O_RDONLY);

    } while (fd < 0 && errno == EINTR);



    fd = TEMP_FAILURE_RETRY(open(filename, O_RDONLY));

    if (fd < 0)

        return -1;

        return NULL;



    /* read the content */

    do {

        len = read(fd, buff, buffsize);

    } while (len < 0 && errno == EINTR);

    /* get its size */

    ret = TEMP_FAILURE_RETRY(fstat(fd, &st));

    if (ret < 0)

        goto EXIT;



    /* Ensure that the size is not ridiculously large */

    length = (size_t)st.st_size;

    if ((off_t)length != st.st_size) {

        errno = ENOMEM;

        goto EXIT;

    }



    /* Memory-map the file now */

    address = TEMP_FAILURE_RETRY(mmap(NULL, length, PROT_READ, MAP_PRIVATE, fd, 0));

    if (address == MAP_FAILED) {

        address = NULL;

        goto EXIT;

    }



    /* We're good, return size */

    *filesize = length;



EXIT:

    /* close the file, preserve old errno for better diagnostics */

    old_errno = errno;

    close(fd);

    errno = old_errno;



    return len;

    return address;

}



/* unmap the file, but preserve errno */

static void

unmap_file(void*  address, size_t  size)

{

    int old_errno = errno;

    TEMP_FAILURE_RETRY(munmap(address, size));

    errno = old_errno;

}



/* Check that a given directory:
@@ -371,18 +392,18 @@ BAD: 
int

get_package_info(const char* pkgName, PackageInfo *info)

{

    static char  buffer[PACKAGES_LIST_BUFFER_SIZE];

    int          buffer_len;

    char*        buffer;

    size_t       buffer_len;

    const char*  p;

    const char*  buffer_end;

    int          result;

    int          result = -1;



    info->uid          = 0;

    info->isDebuggable = 0;

    info->dataDir[0]   = '\0';



    buffer_len = read_file(PACKAGES_LIST_FILE, buffer, sizeof buffer);

    if (buffer_len < 0)

    buffer = map_file(PACKAGES_LIST_FILE, &buffer_len);

    if (buffer == NULL)

        return -1;



    p          = buffer;
@@ -455,7 +476,8 @@ get_package_info(const char* pkgName, PackageInfo *info) 
        string_copy(info->dataDir, sizeof info->dataDir, p, q - p);



        /* Ignore the rest */

        return 0;

        result = 0;

        goto EXIT;



    NEXT_LINE:

        p = next;
@@ -463,9 +485,14 @@ get_package_info(const char* pkgName, PackageInfo *info) 


    /* the package is unknown */

    errno = ENOENT;

    return -1;

    result = -1;

    goto EXIT;



BAD_FORMAT:

    errno = EINVAL;

    return -1;

    result = -1;



EXIT:

    unmap_file(buffer, buffer_len);

    return result;

}