tracing: Fix panic when lseek() called on "trace" opened for writing
The file_ops struct for the "trace" special file defined llseek as seq_lseek(). However, if the file was opened for writing only, seq_open() was not called, and the seek would dereference a null pointer, file->private_data. This patch introduces a new wrapper for seq_lseek() which checks if the file descriptor is opened for reading first. If not, it does nothing. Cc: <stable@kernel.org> Signed-off-by: Slava Pestov <slavapestov@google.com> LKML-Reference: <1290640396-24179-1-git-send-email-slavapestov@google.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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@ -2339,11 +2339,19 @@ tracing_write_stub(struct file *filp, const char __user *ubuf,
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return count;
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return count;
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}
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}
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static loff_t tracing_seek(struct file *file, loff_t offset, int origin)
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{
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if (file->f_mode & FMODE_READ)
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return seq_lseek(file, offset, origin);
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else
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return 0;
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}
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static const struct file_operations tracing_fops = {
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static const struct file_operations tracing_fops = {
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.open = tracing_open,
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.open = tracing_open,
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.read = seq_read,
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.read = seq_read,
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.write = tracing_write_stub,
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.write = tracing_write_stub,
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.llseek = seq_lseek,
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.llseek = tracing_seek,
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.release = tracing_release,
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.release = tracing_release,
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};
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};
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