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authorArtem Bityutskiy <artem.bityutskiy@linux.intel.com>2013-06-28 14:15:14 +0300
committerAl Viro <viro@zeniv.linux.org.uk>2013-06-29 12:45:37 +0400
commit33f1a63ae84dfd9ad298cf275b8f1887043ced36 (patch)
tree4719106331ac4dff7a16d3ab5b7c0b15ef6ec0d1 /samples/hw_breakpoint
parent945fb136dfcb5291b4fb2abd4fd1edf790de44ff (diff)
downloadvexpress-lsk-33f1a63ae84dfd9ad298cf275b8f1887043ced36.tar.gz
UBIFS: prepare to fix a horrid bug
Al Viro pointed me to the fact that '->readdir()' and '->llseek()' have no mutual exclusion, which means the 'ubifs_dir_llseek()' can be run while we are in the middle of 'ubifs_readdir()'. First of all, this means that 'file->private_data' can be freed while 'ubifs_readdir()' uses it. But this particular patch does not fix the problem. This patch is only a preparation, and the fix will follow next. In this patch we make 'ubifs_readdir()' stop using 'file->f_pos' directly, because 'file->f_pos' can be changed by '->llseek()' at any point. This may lead 'ubifs_readdir()' to returning inconsistent data: directory entry names may correspond to incorrect file positions. So here we introduce a local variable 'pos', read 'file->f_pose' once at very the beginning, and then stick to 'pos'. The result of this is that when 'ubifs_dir_llseek()' changes 'file->f_pos' while we are in the middle of 'ubifs_readdir()', the latter "wins". Cc: stable@vger.kernel.org Reported-by: Al Viro <viro@zeniv.linux.org.uk> Tested-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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