From 43807eba1303b4b4606debd444f4fdc93ef560d7 Mon Sep 17 00:00:00 2001 From: Slava Pestov Date: Wed, 24 Nov 2010 15:13:16 -0800 Subject: [PATCH] tracing: Fix panic when lseek() called on "trace" opened for writing commit 364829b1263b44aa60383824e4c1289d83d78ca7 upstream. 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. Signed-off-by: Slava Pestov LKML-Reference: <1290640396-24179-1-git-send-email-slavapestov@google.com> Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 3cfb60b4770b..a2a2d1f02c83 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2199,11 +2199,19 @@ 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, }; -- 2.39.5