UBIFS: fix oops when R/O file-system is fsync'ed
This patch fixes severe UBIFS bug: UBIFS oopses when we 'fsync()' an
file on R/O-mounter file-system. We (the UBIFS authors) incorrectly
thought that VFS would not propagate 'fsync()' down to the file-system
if it is read-only, but this is not the case.
It is easy to exploit this bug using the following simple perl script:
use strict;
use File::Sync qw(fsync sync);
die "File path is not specified" if not defined $ARGV[0];
my $path = $ARGV[0];
open FILE, "<", "$path" or die "Cannot open $path: $!";
fsync(\*FILE) or die "cannot fsync $path: $!";
close FILE or die "Cannot close $path: $!";
Thanks to Reuben Dowle <Reuben.Dowle@navico.com> for reporting about this
issue.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reported-by: Reuben Dowle <Reuben.Dowle@navico.com>
Cc: stable@kernel.org
diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index 28be1e6..b286db7 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -1312,6 +1312,9 @@
dbg_gen("syncing inode %lu", inode->i_ino);
+ if (inode->i_sb->s_flags & MS_RDONLY)
+ return 0;
+
/*
* VFS has already synchronized dirty pages for this inode. Synchronize
* the inode unless this is a 'datasync()' call.