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Subject[BK-PATCH-2.5] NTFS: 2.0.18 - Fix race condition in reading of compressed files
Date
From
Linus, please do a

bk pull http://linux-ntfs.bkbits.net/ntfs-tng-2.5

This fixes a nasty little race condition in reading compressed files. There
was a narrow window between checking a buffer head for being uptodate and
locking it in fs/ntfs/compress.c::ntfs_file_read_compressed_block(). We now
lock the buffer and then check whether it is uptodate or not.

Big thanks go to Andre and Jens for bringing a stable IDE layer to 2.5.25
which actually makes it possible to start finding bugs in other places
other than IDE!

I am running http://www.linuxdiskcert.org/LAD-ide24-2.5.25.patch.bz2 on
top of the current 2.5 BitKeeper tree and it's working great!!! Thanks guys!

Best regards,

Anton
--
Anton Altaparmakov <aia21 at cantab.net> (replace at with @)
Linux NTFS maintainer / IRC: #ntfs on irc.openprojects.net
WWW: http://linux-ntfs.sf.net/, http://www-stu.christs.cam.ac.uk/~aia21/

===================================================================

This will update the following files:

Documentation/filesystems/ntfs.txt | 2 ++
fs/ntfs/ChangeLog | 8 ++++++++
fs/ntfs/Makefile | 2 +-
fs/ntfs/compress.c | 17 +++++++++--------
4 files changed, 20 insertions(+), 9 deletions(-)

through these ChangeSets:

<aia21@cantab.net> (02/07/11 1.621)
NTFS: 2.0.18 - Fix race condition in reading of compressed files.
- There was a narrow window between checking a buffer head for being
uptodate and locking it in ntfs_file_read_compressed_block(). We now
lock the buffer and then check whether it is uptodate or not.


diff -Nru a/Documentation/filesystems/ntfs.txt b/Documentation/filesystems/ntfs.txt
--- a/Documentation/filesystems/ntfs.txt Thu Jul 11 20:19:13 2002
+++ b/Documentation/filesystems/ntfs.txt Thu Jul 11 20:19:13 2002
@@ -247,6 +247,8 @@

Note, a technical ChangeLog aimed at kernel hackers is in fs/ntfs/ChangeLog.

+2.0.18:
+ - Fix race condition in reading of compressed files.
2.0.17:
- Cleanups and optimizations.
2.0.16:
diff -Nru a/fs/ntfs/ChangeLog b/fs/ntfs/ChangeLog
--- a/fs/ntfs/ChangeLog Thu Jul 11 20:19:13 2002
+++ b/fs/ntfs/ChangeLog Thu Jul 11 20:19:13 2002
@@ -13,6 +13,14 @@
with initialized_size < data_size. I don't think it can happen but
it requires more careful consideration.
- Enable NFS exporting of NTFS.
+ - Apply block resolution optimization from aops.c::ntfs_read_block() to
+ compress.c::ntfs_file_read_compressed_block() as well.
+
+2.0.18 - Fix race condition in reading of compressed files.
+
+ - There was a narrow window between checking a buffer head for being
+ uptodate and locking it in ntfs_file_read_compressed_block(). We now
+ lock the buffer and then check whether it is uptodate or not.

2.0.17 - Cleanups and optimizations - shrinking the ToDo list.

diff -Nru a/fs/ntfs/Makefile b/fs/ntfs/Makefile
--- a/fs/ntfs/Makefile Thu Jul 11 20:19:13 2002
+++ b/fs/ntfs/Makefile Thu Jul 11 20:19:13 2002
@@ -5,7 +5,7 @@
ntfs-objs := aops.o attrib.o compress.o debug.o dir.o file.o inode.o mft.o \
mst.o namei.o super.o sysctl.o time.o unistr.o upcase.o

-EXTRA_CFLAGS = -DNTFS_VERSION=\"2.0.17\"
+EXTRA_CFLAGS = -DNTFS_VERSION=\"2.0.18\"

ifeq ($(CONFIG_NTFS_DEBUG),y)
EXTRA_CFLAGS += -DDEBUG
diff -Nru a/fs/ntfs/compress.c b/fs/ntfs/compress.c
--- a/fs/ntfs/compress.c Thu Jul 11 20:19:13 2002
+++ b/fs/ntfs/compress.c Thu Jul 11 20:19:13 2002
@@ -157,7 +157,7 @@

/* Default error code. */
int err = -EOVERFLOW;
-
+
ntfs_debug("Entering, cb_size = 0x%x.", cb_size);
do_next_sb:
ntfs_debug("Beginning sub-block at offset = 0x%x in the cb.",
@@ -193,7 +193,7 @@
/* Setup offsets for the current sub-block destination. */
do_sb_start = *dest_ofs;
do_sb_end = do_sb_start + NTFS_SB_SIZE;
-
+
/* Check that we are still within allowed boundaries. */
if (*dest_index == dest_max_index && do_sb_end > dest_max_ofs)
goto return_overflow;
@@ -572,11 +572,13 @@
for (i = 0; i < nr_bhs; i++) {
struct buffer_head *tbh = bhs[i];

- if (buffer_uptodate(tbh))
+ if (unlikely(test_set_buffer_locked(tbh)))
continue;
-
- lock_buffer(tbh);
- get_bh(tbh);
+ if (unlikely(buffer_uptodate(tbh))) {
+ unlock_buffer(tbh);
+ continue;
+ }
+ atomic_inc(&tbh->b_count);
tbh->b_end_io = end_buffer_io_sync;
submit_bh(READ, tbh);
}
@@ -587,9 +589,8 @@

if (buffer_uptodate(tbh))
continue;
-
wait_on_buffer(tbh);
- if (!buffer_uptodate(tbh))
+ if (unlikely(!buffer_uptodate(tbh)))
goto read_err;
}

===================================================================
This BitKeeper patch contains the following changesets:
+
## Wrapped with gzip_uu ##


begin 664 bkpatch27457
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>+08_/$YA]8]PK4TYGPY2P:(@DC[Y&^KUPD=:#P``
`
end
-
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