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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>
This commit is contained in:
Slava Pestov 2010-11-24 15:13:16 -08:00 committed by Steven Rostedt
parent 60e677373b
commit 364829b126
1 changed files with 9 additions and 1 deletions
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10
kernel/trace/trace.c
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@ -2339,11 +2339,19 @@ tracing_write_stub(struct file *filp, const char __user *ubuf,
return count;
}
static loff_t tracing_seek(struct file *file, loff_t offset, int origin)
{
if (file->f_mode & FMODE_READ)
return seq_lseek(file, offset, origin);
else
return 0;
}
static const struct file_operations tracing_fops = {
.open = tracing_open,
.read = seq_read,
.write = tracing_write_stub,
.llseek = seq_lseek,
.llseek = tracing_seek,
.release = tracing_release,
};