libblkid-tiny: use separated buffer for each block device read

This allows reading multiple chunks of block device data and operating
on them simultaneously. Previous implementation was using a single
buffer (except for reading more data than allocated size) and subsequent
reads were corrupting memory of previously returned buffers.

This fixes e.g. problem with reading NTFS UUID and validating VFAT
signature.

Implementation is based on original libblkid code which handles it
similarly. Buffers are put on probe internal list and freed when
releasing a probe struct.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

diff --git a/libblkid-tiny/libblkid-tiny.c b/libblkid-tiny/libblkid-tiny.c
index a30f6199189a002526c798f62443d3a2e86659ee..05b4b99ef9dc2ac40dc891792b548e90e72cc724 100644 (file)
--- a/libblkid-tiny/libblkid-tiny.c
+++ b/libblkid-tiny/libblkid-tiny.c
@@ -13,9 +13,6 @@
 
 int blkid_debug_mask = 0;
 
-static unsigned char *probe_buffer;
-static unsigned int probe_buffer_size = 0;
-
 int get_linux_version (void)
 {
        static int kver = -1;
@@ -81,32 +78,27 @@ int blkid_probe_sprintf_version(blkid_probe pr, const char *fmt, ...)
 unsigned char *blkid_probe_get_buffer(blkid_probe pr,
                                blkid_loff_t off, blkid_loff_t len)
 {
+       struct blkid_bufinfo *bf;
        int ret;
-       unsigned char *buf;
-
-       if (len > probe_buffer_size) {
-               buf = realloc(probe_buffer, len);
 
-               if (!buf) {
-                       fprintf(stderr, "failed to allocate %d byte buffer\n",
-                               (int)len);
-
-                       return NULL;
-               }
-
-               probe_buffer = buf;
-               probe_buffer_size = len;
-       }
-
-       memset(probe_buffer, 0, probe_buffer_size);
+       bf = malloc(sizeof(*bf) + len);
+       if (!bf)
+               return NULL;
+       memset(bf, 0, sizeof(*bf));
+       bf->data = ((unsigned char *)bf) + sizeof(*bf);
 
        lseek(pr->fd, off, SEEK_SET);
-       ret = read(pr->fd, probe_buffer, len);
+       ret = read(pr->fd, bf->data, len);
 
-       if (ret != len)
+       if (ret != len) {
                fprintf(stderr, "faile to read blkid\n");
+               free(bf);
+               return NULL;
+       }
+
+       list_add_tail(&bf->bufs, &pr->buffers);
 
-       return probe_buffer;
+       return bf->data;
 }
 
 int blkid_probe_set_label(blkid_probe pr, unsigned char *label, size_t len)

diff --git a/libblkid-tiny/libblkid-tiny.h b/libblkid-tiny/libblkid-tiny.h
index 06ff94bf8a662c357ca4f2d7c5cd9e5bc19adab8..aa87fd9a225a1ec363346658d995def4d9342351 100644 (file)
--- a/libblkid-tiny/libblkid-tiny.h
+++ b/libblkid-tiny/libblkid-tiny.h
@@ -58,6 +58,8 @@ struct blkid_struct_probe
        char    uuid[64];
        char    label[256];
        char    version[64];
+
+       struct list_head        buffers;        /* list of buffers */
 };
 
 struct blkid_struct_probe *blkid_new_probe(void);

diff --git a/libblkid-tiny/probe.c b/libblkid-tiny/probe.c
index 54e22dcb441cf796f572e5a1615362076a44e56c..ae7e7088f36d39556ce8411b5e5d09f2e053be63 100644 (file)
--- a/libblkid-tiny/probe.c
+++ b/libblkid-tiny/probe.c
@@ -9,8 +9,11 @@
 
 #include <stdlib.h>
 
+#include "blkidP.h"
 #include "libblkid-tiny.h"
 
+static int blkid_probe_reset_buffers(struct blkid_struct_probe *pr);
+
 struct blkid_struct_probe *blkid_new_probe(void)
 {
        struct blkid_struct_probe *pr;
@@ -19,6 +22,8 @@ struct blkid_struct_probe *blkid_new_probe(void)
        if (!pr)
                return NULL;
 
+       INIT_LIST_HEAD(&pr->buffers);
+
        return pr;
 }
 
@@ -27,5 +32,23 @@ void blkid_free_probe(struct blkid_struct_probe *pr)
        if (!pr)
                return;
 
+       blkid_probe_reset_buffers(pr);
+
        free(pr);
 }
+
+static int blkid_probe_reset_buffers(struct blkid_struct_probe *pr)
+{
+       if (list_empty(&pr->buffers))
+               return 0;
+
+       while (!list_empty(&pr->buffers)) {
+               struct blkid_bufinfo *bf = list_first_entry(&pr->buffers, struct blkid_bufinfo, bufs);
+
+               list_del(&bf->bufs);
+
+               free(bf);
+       }
+
+       return 0;
+}