Mesa (master): util/disk_cache: don't deadlock on premature EOF

[Timothy Arceri]

Module: Mesa
Branch: master
Commit: b9e92334f79bff2497fd718d49fe7c53b5f2074c
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=b9e92334f79bff2497fd718d49fe7c53b5f2074c

Author: Grazvydas Ignotas <notasas at gmail.com>
Date:   Sat Mar 25 01:58:42 2017 +0200

util/disk_cache: don't deadlock on premature EOF

If we get EOF earlier than expected, the current read loops will
deadlock. This may easily happen if the disk cache gets corrupted.
Fix it by using a helper function that handles EOF.

Steps to reproduce (on a build with asserts disabled):
$ glxgears
$ find ~/.cache/mesa/ -type f -exec truncate -s 0 '{}' \;
$ glxgears # deadlock

Signed-off-by: Grazvydas Ignotas <notasas at gmail.com>
Reviewed-by: Timothy Arceri <tarceri at itsqueeze.com>

---

 src/util/disk_cache.c | 43 ++++++++++++++++++++++++++-----------------
 1 file changed, 26 insertions(+), 17 deletions(-)

diff --git a/src/util/disk_cache.c b/src/util/disk_cache.c
index a9a3e594bc..d9de8ef6e4 100644
--- a/src/util/disk_cache.c
+++ b/src/util/disk_cache.c
@@ -642,6 +642,21 @@ disk_cache_remove(struct disk_cache *cache, const cache_key key)
 }
 
 static ssize_t
+read_all(int fd, void *buf, size_t count)
+{
+   char *in = buf;
+   ssize_t read_ret;
+   size_t done;
+
+   for (done = 0; done < count; done += read_ret) {
+      read_ret = read(fd, in + done, count - done);
+      if (read_ret == -1 || read_ret == 0)
+         return -1;
+   }
+   return done;
+}
+
+static ssize_t
 write_all(int fd, const void *buf, size_t count)
 {
    const char *out = buf;
@@ -938,7 +953,7 @@ inflate_cache_data(uint8_t *in_data, size_t in_data_size,
 void *
 disk_cache_get(struct disk_cache *cache, const cache_key key, size_t *size)
 {
-   int fd = -1, ret, len;
+   int fd = -1, ret;
    struct stat sb;
    char *filename = NULL;
    uint8_t *data = NULL;
@@ -969,12 +984,10 @@ disk_cache_get(struct disk_cache *cache, const cache_key key, size_t *size)
       goto fail;
 
    assert(sb.st_size > ck_size);
-   for (len = 0; len < ck_size; len += ret) {
-      ret = read(fd, ((uint8_t *) file_header) + len, ck_size - len);
-      if (ret == -1) {
-         free(file_header);
-         goto fail;
-      }
+   ret = read_all(fd, file_header, ck_size);
+   if (ret == -1) {
+      free(file_header);
+      goto fail;
    }
 
    assert(memcmp(cache->driver_keys_blob, file_header, ck_size) == 0);
@@ -992,19 +1005,15 @@ disk_cache_get(struct disk_cache *cache, const cache_key key, size_t *size)
    /* Load the CRC that was created when the file was written. */
    struct cache_entry_file_data cf_data;
    size_t cf_data_size = sizeof(cf_data);
-   for (len = 0; len < cf_data_size; len += ret) {
-      ret = read(fd, ((uint8_t *) &cf_data) + len, cf_data_size - len);
-      if (ret == -1)
-         goto fail;
-   }
+   ret = read_all(fd, &cf_data, cf_data_size);
+   if (ret == -1)
+      goto fail;
 
    /* Load the actual cache data. */
    size_t cache_data_size = sb.st_size - cf_data_size - ck_size;
-   for (len = 0; len < cache_data_size; len += ret) {
-      ret = read(fd, data + len, cache_data_size - len);
-      if (ret == -1)
-         goto fail;
-   }
+   ret = read_all(fd, data, cache_data_size);
+   if (ret == -1)
+      goto fail;
 
    /* Uncompress the cache data */
    uncompressed_data = malloc(cf_data.uncompressed_size);