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
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@ -1312,6 +1312,9 @@ int ubifs_fsync(struct file *file, int datasync)
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dbg_gen("syncing inode %lu", inode->i_ino);
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if (inode->i_sb->s_flags & MS_RDONLY)
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return 0;
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/*
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* VFS has already synchronized dirty pages for this inode. Synchronize
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* the inode unless this is a 'datasync()' call.
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