Re: [U-Boot] [PATCH] fs: ext4: Prevent infinite loop in ext4fs_iterate_dir

[Stefan Roese]

Hi Thomas,

On 18.11.2015 18:42, Thomas Fitzsimmons wrote:

If the ext3 journal gets out of sync with what is written on disk, for
example because of an unexpected power cut, ext4fs_read_file can
return an all-zero directory entry.  In that case, ext4fs_iterate_dir
would infinite loop.

This patch detects when a directory entry's direntlen member is 0 and
returns a failure status, which breaks out of the infinite loop.  As a
result, U-Boot will not find files that may subsequently be recovered
when the journal is replayed.

This is better behaviour than hanging in an infinite loop, but as a
further improvement maybe U-Boot could interpret the ext3 journal and
actually find the unsynced entries.

Signed-off-by: Thomas Fitzsimmons 
---
  fs/ext4/ext4_common.c | 5 +
  1 file changed, 5 insertions(+)

diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c
index 727a2f7..e73223a 100644
--- a/fs/ext4/ext4_common.c
+++ b/fs/ext4/ext4_common.c
@@ -1920,6 +1920,11 @@ int ext4fs_iterate_dir(struct ext2fs_node *dir, char 
*name,
if (status < 0)
return 0;

+   if (dirent.direntlen == 0) {
+   printf("Failed to iterate over directory %s\n", name);
+   return 0;
+   }
+
if (dirent.namelen != 0) {
char filename[dirent.namelen + 1];
struct ext2fs_node *fdiro;



Reviewed-by: Stefan Roese 

Thanks,
Stefan
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[U-Boot] [PATCH] fs: ext4: Prevent infinite loop in ext4fs_iterate_dir

[Thomas Fitzsimmons]

If the ext3 journal gets out of sync with what is written on disk, for
example because of an unexpected power cut, ext4fs_read_file can
return an all-zero directory entry.  In that case, ext4fs_iterate_dir
would infinite loop.

This patch detects when a directory entry's direntlen member is 0 and
returns a failure status, which breaks out of the infinite loop.  As a
result, U-Boot will not find files that may subsequently be recovered
when the journal is replayed.

This is better behaviour than hanging in an infinite loop, but as a
further improvement maybe U-Boot could interpret the ext3 journal and
actually find the unsynced entries.

Signed-off-by: Thomas Fitzsimmons 
---
 fs/ext4/ext4_common.c | 5 +
 1 file changed, 5 insertions(+)

diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c
index 727a2f7..e73223a 100644
--- a/fs/ext4/ext4_common.c
+++ b/fs/ext4/ext4_common.c
@@ -1920,6 +1920,11 @@ int ext4fs_iterate_dir(struct ext2fs_node *dir, char 
*name,
if (status < 0)
return 0;
 
+   if (dirent.direntlen == 0) {
+   printf("Failed to iterate over directory %s\n", name);
+   return 0;
+   }
+
if (dirent.namelen != 0) {
char filename[dirent.namelen + 1];
struct ext2fs_node *fdiro;
-- 
1.8.3.1

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