[Qemu-devel] [PATCH v3 0/6] Update filename string sizes in block layer

[Qemu-devel] [PATCH v3 0/6] Update filename string sizes in block layer

[Jeff Cody]

The block layer uses a mixture of 'PATH_MAX' and '1024' string sizes
for filenames (and backing filenames).

This series consolidates all that usage to 'PATH_MAX'.  Since most platforms
(especially the most common platforms for QEMU) have a PATH_MAX larger than
1024 bytes, this series also changes stack allocations of PATH_MAX to be
dynamically allocated.

Note: checkpatch.pl complains about an extra space in a printf in
      patches 1 & 2.  The lines complained about are in the diff context and
      not the actual changes, so I did not fix them up to satisfy checkpatch.

Changes from v3:
    - simplified extent_path handling in vmdk_parse_extents() (Thanks Stefan)
    - moved declaration of backing_filename2 to inside if
      statement in bdrv_query_image_info() (Thanks Stefan)
    - removed zombie variable in bdrv_commit (Thanks Stefan)
    - fixed typo in commit message (Thanks Stefan)

Changes from v2:

    - Change stack allocations to dybnamic (Thanks Kevin)
    - Update qcow/qcow2 ti perform safety checks for platforms that
      have a PATH_MAX < 1024 (thanks John, Kevin).

Jeff Cody (6):
  block: vmdk - make ret variable usage clear
  block: vmdk - move string allocations from stack to the heap
  block: qapi - move string allocation from stack to the heap
  block: remove unused variable in bdrv_commit
  block: mirror - change string allocation to 2-bytes
  block: update string sizes for filename,backing_file,exact_filename

 block.c                   |  3 ---
 block/mirror.c            |  3 ++-
 block/qapi.c              |  7 ++++---
 block/qcow.c              |  2 +-
 block/qcow2.c             |  3 ++-
 block/vmdk.c              | 51 ++++++++++++++++++++++++++++-------------------
 block/vvfat.c             |  4 ++--
 include/block/block_int.h |  8 ++++----
 qemu-img.c                |  4 ++--
 9 files changed, 47 insertions(+), 38 deletions(-)

-- 
1.9.3

[Qemu-devel] [PATCH v3 1/6] block: vmdk - make ret variable usage clear

[Jeff Cody]

Keep the variable 'ret' something that is returned by the function it is
defined in.  For the return value of 'sscanf', use a more meaningful
variable name.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
---
 block/vmdk.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/block/vmdk.c b/block/vmdk.c
index 52cb888..dc6459c 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -785,6 +785,7 @@ static int vmdk_parse_extents(const char *desc, BlockDriverState *bs,
                               const char *desc_file_path, Error **errp)
 {
     int ret;
+    int matches;
     char access[11];
     char type[11];
     char fname[512];
@@ -796,6 +797,7 @@ static int vmdk_parse_extents(const char *desc, BlockDriverState *bs,
     BDRVVmdkState *s = bs->opaque;
     VmdkExtent *extent;
 
+
     while (*p) {
         /* parse extent line in one of below formats:
          *
@@ -805,23 +807,23 @@ static int vmdk_parse_extents(const char *desc, BlockDriverState *bs,
          * RW [size in sectors] VMFSSPARSE "file-name.vmdk"
          */
         flat_offset = -1;
-        ret = sscanf(p, "%10s %" SCNd64 " %10s \"%511[^\n\r\"]\" %" SCNd64,
-                access, &sectors, type, fname, &flat_offset);
-        if (ret < 4 || strcmp(access, "RW")) {
+        matches = sscanf(p, "%10s %" SCNd64 " %10s \"%511[^\n\r\"]\" %" SCNd64,
+                         access, &sectors, type, fname, &flat_offset);
+        if (matches < 4 || strcmp(access, "RW")) {
             goto next_line;
         } else if (!strcmp(type, "FLAT")) {
-            if (ret != 5 || flat_offset < 0) {
+            if (matches != 5 || flat_offset < 0) {
                 error_setg(errp, "Invalid extent lines: \n%s", p);
                 return -EINVAL;
             }
         } else if (!strcmp(type, "VMFS")) {
-            if (ret == 4) {
+            if (matches == 4) {
                 flat_offset = 0;
             } else {
                 error_setg(errp, "Invalid extent lines:\n%s", p);
                 return -EINVAL;
             }
-        } else if (ret != 4) {
+        } else if (matches != 4) {
             error_setg(errp, "Invalid extent lines:\n%s", p);
             return -EINVAL;
         }
-- 
1.9.3

[Qemu-devel] [PATCH v3 2/6] block: vmdk - move string allocations from stack to the heap

[Jeff Cody]

Functions 'vmdk_parse_extents' and 'vmdk_create' allocate several
PATH_MAX sized arrays on the stack.  Make these dynamically allocated.

Signed-off-by: Jeff Cody <jcody@redhat.com>
---
 block/vmdk.c | 39 +++++++++++++++++++++++----------------
 1 file changed, 23 insertions(+), 16 deletions(-)

diff --git a/block/vmdk.c b/block/vmdk.c
index dc6459c..7d079ad 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -792,12 +792,11 @@ static int vmdk_parse_extents(const char *desc, BlockDriverState *bs,
     const char *p = desc;
     int64_t sectors = 0;
     int64_t flat_offset;
-    char extent_path[PATH_MAX];
+    char *extent_path;
     BlockDriverState *extent_file;
     BDRVVmdkState *s = bs->opaque;
     VmdkExtent *extent;
 
-
     while (*p) {
         /* parse extent line in one of below formats:
          *
@@ -843,11 +842,13 @@ static int vmdk_parse_extents(const char *desc, BlockDriverState *bs,
             return -EINVAL;
         }
 
+        extent_path = g_malloc0(PATH_MAX);
         path_combine(extent_path, sizeof(extent_path),
                 desc_file_path, fname);
         extent_file = NULL;
         ret = bdrv_open(&extent_file, extent_path, NULL, NULL,
                         bs->open_flags | BDRV_O_PROTOCOL, NULL, errp);
+        g_free(extent_path);
         if (ret) {
             return ret;
         }
@@ -1797,10 +1798,15 @@ static int vmdk_create(const char *filename, QemuOpts *opts, Error **errp)
     int ret = 0;
     bool flat, split, compress;
     GString *ext_desc_lines;
-    char path[PATH_MAX], prefix[PATH_MAX], postfix[PATH_MAX];
+    char *path = g_malloc0(PATH_MAX);
+    char *prefix = g_malloc0(PATH_MAX);
+    char *postfix = g_malloc0(PATH_MAX);
+    char *desc_line = g_malloc0(BUF_SIZE);
+    char *ext_filename = g_malloc0(PATH_MAX);
+    char *desc_filename = g_malloc0(PATH_MAX);
     const int64_t split_size = 0x80000000;  /* VMDK has constant split size */
     const char *desc_extent_line;
-    char parent_desc_line[BUF_SIZE] = "";
+    char *parent_desc_line = g_malloc0(BUF_SIZE);
     uint32_t parent_cid = 0xffffffff;
     uint32_t number_heads = 16;
     bool zeroed_grain = false;
@@ -1916,33 +1922,27 @@ static int vmdk_create(const char *filename, QemuOpts *opts, Error **errp)
         }
         parent_cid = vmdk_read_cid(bs, 0);
         bdrv_unref(bs);
-        snprintf(parent_desc_line, sizeof(parent_desc_line),
+        snprintf(parent_desc_line, BUF_SIZE,
                 "parentFileNameHint=\"%s\"", backing_file);
     }
 
     /* Create extents */
     filesize = total_size;
     while (filesize > 0) {
-        char desc_line[BUF_SIZE];
-        char ext_filename[PATH_MAX];
-        char desc_filename[PATH_MAX];
         int64_t size = filesize;
 
         if (split && size > split_size) {
             size = split_size;
         }
         if (split) {
-            snprintf(desc_filename, sizeof(desc_filename), "%s-%c%03d%s",
+            snprintf(desc_filename, PATH_MAX, "%s-%c%03d%s",
                     prefix, flat ? 'f' : 's', ++idx, postfix);
         } else if (flat) {
-            snprintf(desc_filename, sizeof(desc_filename), "%s-flat%s",
-                    prefix, postfix);
+            snprintf(desc_filename, PATH_MAX, "%s-flat%s", prefix, postfix);
         } else {
-            snprintf(desc_filename, sizeof(desc_filename), "%s%s",
-                    prefix, postfix);
+            snprintf(desc_filename, PATH_MAX, "%s%s", prefix, postfix);
         }
-        snprintf(ext_filename, sizeof(ext_filename), "%s%s",
-                path, desc_filename);
+        snprintf(ext_filename, PATH_MAX, "%s%s", path, desc_filename);
 
         if (vmdk_create_extent(ext_filename, size,
                                flat, compress, zeroed_grain, opts, errp)) {
@@ -1952,7 +1952,7 @@ static int vmdk_create(const char *filename, QemuOpts *opts, Error **errp)
         filesize -= size;
 
         /* Format description line */
-        snprintf(desc_line, sizeof(desc_line),
+        snprintf(desc_line, BUF_SIZE,
                     desc_extent_line, size / BDRV_SECTOR_SIZE, desc_filename);
         g_string_append(ext_desc_lines, desc_line);
     }
@@ -2007,6 +2007,13 @@ exit:
     g_free(backing_file);
     g_free(fmt);
     g_free(desc);
+    g_free(path);
+    g_free(prefix);
+    g_free(postfix);
+    g_free(desc_line);
+    g_free(ext_filename);
+    g_free(desc_filename);
+    g_free(parent_desc_line);
     g_string_free(ext_desc_lines, true);
     return ret;
 }
-- 
1.9.3

Re: [Qemu-devel] [PATCH v3 2/6] block: vmdk - move string allocations from stack to the heap

[Paolo Bonzini]

On 22/01/2015 14:03, Jeff Cody wrote:
> Functions 'vmdk_parse_extents' and 'vmdk_create' allocate several
> PATH_MAX sized arrays on the stack.  Make these dynamically allocated.
> 
> Signed-off-by: Jeff Cody <jcody@redhat.com>
> ---
>  block/vmdk.c | 39 +++++++++++++++++++++++----------------
>  1 file changed, 23 insertions(+), 16 deletions(-)
> 
> diff --git a/block/vmdk.c b/block/vmdk.c
> index dc6459c..7d079ad 100644
> --- a/block/vmdk.c
> +++ b/block/vmdk.c
> @@ -792,12 +792,11 @@ static int vmdk_parse_extents(const char *desc, BlockDriverState *bs,
>      const char *p = desc;
>      int64_t sectors = 0;
>      int64_t flat_offset;
> -    char extent_path[PATH_MAX];
> +    char *extent_path;
>      BlockDriverState *extent_file;
>      BDRVVmdkState *s = bs->opaque;
>      VmdkExtent *extent;
>  
> -
>      while (*p) {
>          /* parse extent line in one of below formats:
>           *
> @@ -843,11 +842,13 @@ static int vmdk_parse_extents(const char *desc, BlockDriverState *bs,
>              return -EINVAL;
>          }
>  
> +        extent_path = g_malloc0(PATH_MAX);
>          path_combine(extent_path, sizeof(extent_path),

Oops, sizeof(extent_path) changed from PATH_MAX to sizeof(char*).
Coverity found this instance, I didn't check for others.

Paolo

>                  desc_file_path, fname);
>          extent_file = NULL;
>          ret = bdrv_open(&extent_file, extent_path, NULL, NULL,
>                          bs->open_flags | BDRV_O_PROTOCOL, NULL, errp);
> +        g_free(extent_path);
>          if (ret) {
>              return ret;
>          }
> @@ -1797,10 +1798,15 @@ static int vmdk_create(const char *filename, QemuOpts *opts, Error **errp)
>      int ret = 0;
>      bool flat, split, compress;
>      GString *ext_desc_lines;
> -    char path[PATH_MAX], prefix[PATH_MAX], postfix[PATH_MAX];
> +    char *path = g_malloc0(PATH_MAX);
> +    char *prefix = g_malloc0(PATH_MAX);
> +    char *postfix = g_malloc0(PATH_MAX);
> +    char *desc_line = g_malloc0(BUF_SIZE);
> +    char *ext_filename = g_malloc0(PATH_MAX);
> +    char *desc_filename = g_malloc0(PATH_MAX);
>      const int64_t split_size = 0x80000000;  /* VMDK has constant split size */
>      const char *desc_extent_line;
> -    char parent_desc_line[BUF_SIZE] = "";
> +    char *parent_desc_line = g_malloc0(BUF_SIZE);
>      uint32_t parent_cid = 0xffffffff;
>      uint32_t number_heads = 16;
>      bool zeroed_grain = false;
> @@ -1916,33 +1922,27 @@ static int vmdk_create(const char *filename, QemuOpts *opts, Error **errp)
>          }
>          parent_cid = vmdk_read_cid(bs, 0);
>          bdrv_unref(bs);
> -        snprintf(parent_desc_line, sizeof(parent_desc_line),
> +        snprintf(parent_desc_line, BUF_SIZE,
>                  "parentFileNameHint=\"%s\"", backing_file);
>      }
>  
>      /* Create extents */
>      filesize = total_size;
>      while (filesize > 0) {
> -        char desc_line[BUF_SIZE];
> -        char ext_filename[PATH_MAX];
> -        char desc_filename[PATH_MAX];
>          int64_t size = filesize;
>  
>          if (split && size > split_size) {
>              size = split_size;
>          }
>          if (split) {
> -            snprintf(desc_filename, sizeof(desc_filename), "%s-%c%03d%s",
> +            snprintf(desc_filename, PATH_MAX, "%s-%c%03d%s",
>                      prefix, flat ? 'f' : 's', ++idx, postfix);
>          } else if (flat) {
> -            snprintf(desc_filename, sizeof(desc_filename), "%s-flat%s",
> -                    prefix, postfix);
> +            snprintf(desc_filename, PATH_MAX, "%s-flat%s", prefix, postfix);
>          } else {
> -            snprintf(desc_filename, sizeof(desc_filename), "%s%s",
> -                    prefix, postfix);
> +            snprintf(desc_filename, PATH_MAX, "%s%s", prefix, postfix);
>          }
> -        snprintf(ext_filename, sizeof(ext_filename), "%s%s",
> -                path, desc_filename);
> +        snprintf(ext_filename, PATH_MAX, "%s%s", path, desc_filename);
>  
>          if (vmdk_create_extent(ext_filename, size,
>                                 flat, compress, zeroed_grain, opts, errp)) {
> @@ -1952,7 +1952,7 @@ static int vmdk_create(const char *filename, QemuOpts *opts, Error **errp)
>          filesize -= size;
>  
>          /* Format description line */
> -        snprintf(desc_line, sizeof(desc_line),
> +        snprintf(desc_line, BUF_SIZE,
>                      desc_extent_line, size / BDRV_SECTOR_SIZE, desc_filename);
>          g_string_append(ext_desc_lines, desc_line);
>      }
> @@ -2007,6 +2007,13 @@ exit:
>      g_free(backing_file);
>      g_free(fmt);
>      g_free(desc);
> +    g_free(path);
> +    g_free(prefix);
> +    g_free(postfix);
> +    g_free(desc_line);
> +    g_free(ext_filename);
> +    g_free(desc_filename);
> +    g_free(parent_desc_line);
>      g_string_free(ext_desc_lines, true);
>      return ret;
>  }
> 

[Qemu-devel] [PATCH v3 3/6] block: qapi - move string allocation from stack to the heap

[Jeff Cody]

Rather than declaring 'backing_filename2' on the stack in
bdrv_query_image_info(), dynamically allocate it on the heap.

Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
---
 block/qapi.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/block/qapi.c b/block/qapi.c
index a6fd6f7..dec9f60 100644
--- a/block/qapi.c
+++ b/block/qapi.c
@@ -175,7 +175,6 @@ void bdrv_query_image_info(BlockDriverState *bs,
 {
     int64_t size;
     const char *backing_filename;
-    char backing_filename2[1024];
     BlockDriverInfo bdi;
     int ret;
     Error *err = NULL;
@@ -211,13 +210,14 @@ void bdrv_query_image_info(BlockDriverState *bs,
 
     backing_filename = bs->backing_file;
     if (backing_filename[0] != '\0') {
+        char *backing_filename2 = g_malloc0(1024);
         info->backing_filename = g_strdup(backing_filename);
         info->has_backing_filename = true;
-        bdrv_get_full_backing_filename(bs, backing_filename2,
-                                       sizeof(backing_filename2), &err);
+        bdrv_get_full_backing_filename(bs, backing_filename2, 1024, &err);
         if (err) {
             error_propagate(errp, err);
             qapi_free_ImageInfo(info);
+            g_free(backing_filename2);
             return;
         }
 
@@ -231,6 +231,7 @@ void bdrv_query_image_info(BlockDriverState *bs,
             info->backing_filename_format = g_strdup(bs->backing_format);
             info->has_backing_filename_format = true;
         }
+        g_free(backing_filename2);
     }
 
     ret = bdrv_query_snapshot_info_list(bs, &info->snapshots, &err);
-- 
1.9.3

[Qemu-devel] [PATCH v3 4/6] block: remove unused variable in bdrv_commit

[Jeff Cody]

As Stefan pointed out, the variable 'filename' in bdrv_commit is unused,
despite being maintained in previous patches.

With this patch, get rid of the variable for good.

Signed-off-by: Jeff Cody <jcody@redhat.com>
---
 block.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/block.c b/block.c
index cbe4a32..d45e4dd 100644
--- a/block.c
+++ b/block.c
@@ -2207,7 +2207,6 @@ int bdrv_commit(BlockDriverState *bs)
     int n, ro, open_flags;
     int ret = 0;
     uint8_t *buf = NULL;
-    char filename[PATH_MAX];
 
     if (!drv)
         return -ENOMEDIUM;
@@ -2222,8 +2221,6 @@ int bdrv_commit(BlockDriverState *bs)
     }
 
     ro = bs->backing_hd->read_only;
-    /* Use pstrcpy (not strncpy): filename must be NUL-terminated. */
-    pstrcpy(filename, sizeof(filename), bs->backing_hd->filename);
     open_flags =  bs->backing_hd->open_flags;
 
     if (ro) {
-- 
1.9.3

[Qemu-devel] [PATCH v3 5/6] block: mirror - change string allocation to 2-bytes

[Jeff Cody]

The backing_filename string in mirror_run() is only used to check
for a NULL string, so we don't need to allocate 1024 bytes (or, later,
PATH_MAX bytes), when we only need to copy the first 2 characters.

We technically only need 1 byte, as we are just checking for NULL, but
since backing_filename[] is populated by bdrv_get_backing_filename(), a
string size of 1 will always only return '\0';

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
---
 block/mirror.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/mirror.c b/block/mirror.c
index 9019d1b..4056164 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -378,7 +378,8 @@ static void coroutine_fn mirror_run(void *opaque)
     int64_t sector_num, end, sectors_per_chunk, length;
     uint64_t last_pause_ns;
     BlockDriverInfo bdi;
-    char backing_filename[1024];
+    char backing_filename[2]; /* we only need 2 characters because we are only
+                                 checking for a NULL string */
     int ret = 0;
     int n;
 
-- 
1.9.3

[Qemu-devel] [PATCH v3 6/6] block: update string sizes for filename, backing_file, exact_filename

[Jeff Cody]

The string field entries 'filename', 'backing_file', and
'exact_filename' in the BlockDriverState struct are defined as 1024
bytes.

However, many places that use these values accept a maximum of PATH_MAX
bytes, so we have a mixture of 1024 byte and PATH_MAX byte allocations.
This patch makes the BlockDriverStruct field string sizes match usage.

This patch also does a few fixes related to the size that needs to
happen now:

    * the block qapi driver is updated to use PATH_MAX bytes
    * the qcow and qcow2 drivers have an additional safety check
    * the block vvfat driver is updated to use PATH_MAX bytes
      for the size of backing_file, for systems where PATH_MAX is < 1024
      bytes.
    * qemu-img uses PATH_MAX rather than 1024.  These instances were not
      changed to be dynamically allocated, however, as the extra
      temporary 3K in stack usage for qemu-img does not seem worrisome.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
---
 block/qapi.c              | 4 ++--
 block/qcow.c              | 2 +-
 block/qcow2.c             | 3 ++-
 block/vvfat.c             | 4 ++--
 include/block/block_int.h | 8 ++++----
 qemu-img.c                | 4 ++--
 6 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/block/qapi.c b/block/qapi.c
index dec9f60..75c388e 100644
--- a/block/qapi.c
+++ b/block/qapi.c
@@ -210,10 +210,10 @@ void bdrv_query_image_info(BlockDriverState *bs,
 
     backing_filename = bs->backing_file;
     if (backing_filename[0] != '\0') {
-        char *backing_filename2 = g_malloc0(1024);
+        char *backing_filename2 = g_malloc0(PATH_MAX);
         info->backing_filename = g_strdup(backing_filename);
         info->has_backing_filename = true;
-        bdrv_get_full_backing_filename(bs, backing_filename2, 1024, &err);
+        bdrv_get_full_backing_filename(bs, backing_filename2, PATH_MAX, &err);
         if (err) {
             error_propagate(errp, err);
             qapi_free_ImageInfo(info);
diff --git a/block/qcow.c b/block/qcow.c
index ece2269..ccbe9e0 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -215,7 +215,7 @@ static int qcow_open(BlockDriverState *bs, QDict *options, int flags,
     /* read the backing file name */
     if (header.backing_file_offset != 0) {
         len = header.backing_file_size;
-        if (len > 1023) {
+        if (len > 1023 || len > sizeof(bs->backing_file)) {
             error_setg(errp, "Backing file name too long");
             ret = -EINVAL;
             goto fail;
diff --git a/block/qcow2.c b/block/qcow2.c
index e4e690a..dbaf016 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -868,7 +868,8 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
     /* read the backing file name */
     if (header.backing_file_offset != 0) {
         len = header.backing_file_size;
-        if (len > MIN(1023, s->cluster_size - header.backing_file_offset)) {
+        if (len > MIN(1023, s->cluster_size - header.backing_file_offset) ||
+            len > sizeof(bs->backing_file)) {
             error_setg(errp, "Backing file name too long");
             ret = -EINVAL;
             goto fail;
diff --git a/block/vvfat.c b/block/vvfat.c
index e34a789..a1a44f0 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -2909,8 +2909,8 @@ static int enable_write_target(BDRVVVFATState *s, Error **errp)
 
     array_init(&(s->commits), sizeof(commit_t));
 
-    s->qcow_filename = g_malloc(1024);
-    ret = get_tmp_filename(s->qcow_filename, 1024);
+    s->qcow_filename = g_malloc(PATH_MAX);
+    ret = get_tmp_filename(s->qcow_filename, PATH_MAX);
     if (ret < 0) {
         error_setg_errno(errp, -ret, "can't create temporary file");
         goto err;
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 06a21dd..e264be9 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -339,13 +339,13 @@ struct BlockDriverState {
      * regarding this BDS's context */
     QLIST_HEAD(, BdrvAioNotifier) aio_notifiers;
 
-    char filename[1024];
-    char backing_file[1024]; /* if non zero, the image is a diff of
-                                this file image */
+    char filename[PATH_MAX];
+    char backing_file[PATH_MAX]; /* if non zero, the image is a diff of
+                                    this file image */
     char backing_format[16]; /* if non-zero and backing_file exists */
 
     QDict *full_open_options;
-    char exact_filename[1024];
+    char exact_filename[PATH_MAX];
 
     BlockDriverState *backing_hd;
     BlockDriverState *file;
diff --git a/qemu-img.c b/qemu-img.c
index 7876258..4e9a7f5 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -2556,7 +2556,7 @@ static int img_rebase(int argc, char **argv)
 
     /* For safe rebasing we need to compare old and new backing file */
     if (!unsafe) {
-        char backing_name[1024];
+        char backing_name[PATH_MAX];
 
         blk_old_backing = blk_new_with_bs("old_backing", &error_abort);
         bs_old_backing = blk_bs(blk_old_backing);
@@ -2614,7 +2614,7 @@ static int img_rebase(int argc, char **argv)
         }
         old_backing_num_sectors = bdrv_nb_sectors(bs_old_backing);
         if (old_backing_num_sectors < 0) {
-            char backing_name[1024];
+            char backing_name[PATH_MAX];
 
             bdrv_get_backing_filename(bs, backing_name, sizeof(backing_name));
             error_report("Could not get size of '%s': %s",
-- 
1.9.3

Re: [Qemu-devel] [PATCH v3 0/6] Update filename string sizes in block layer

[Kevin Wolf]

Am 22.01.2015 um 14:03 hat Jeff Cody geschrieben:
> The block layer uses a mixture of 'PATH_MAX' and '1024' string sizes
> for filenames (and backing filenames).
> 
> This series consolidates all that usage to 'PATH_MAX'.  Since most platforms
> (especially the most common platforms for QEMU) have a PATH_MAX larger than
> 1024 bytes, this series also changes stack allocations of PATH_MAX to be
> dynamically allocated.
> 
> Note: checkpatch.pl complains about an extra space in a printf in
>       patches 1 & 2.  The lines complained about are in the diff context and
>       not the actual changes, so I did not fix them up to satisfy checkpatch.
> 
> Changes from v3:
>     - simplified extent_path handling in vmdk_parse_extents() (Thanks Stefan)
>     - moved declaration of backing_filename2 to inside if
>       statement in bdrv_query_image_info() (Thanks Stefan)
>     - removed zombie variable in bdrv_commit (Thanks Stefan)
>     - fixed typo in commit message (Thanks Stefan)
> 
> Changes from v2:
> 
>     - Change stack allocations to dybnamic (Thanks Kevin)
>     - Update qcow/qcow2 ti perform safety checks for platforms that
>       have a PATH_MAX < 1024 (thanks John, Kevin).

Thanks, applied to the block branch.

Kevin