| From | Andi Kleen <> | Subject | [PATCH] [88/139] tracing: Fix panic when lseek() called on "trace" opened for writing | Date | Tue, 1 Feb 2011 16:44:45 -0800 (PST) |
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2.6.35-longterm review patch. If anyone has any objections, please let me know.
------------------ From: Slava Pestov <slavapestov@google.com>
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 <slavapestov@google.com> Signed-off-by: Andi Kleen <ak@linux.intel.com> LKML-Reference: <1290640396-24179-1-git-send-email-slavapestov@google.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- kernel/trace/trace.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
Index: linux-2.6.35.y/kernel/trace/trace.c =================================================================== --- linux-2.6.35.y.orig/kernel/trace/trace.c +++ linux-2.6.35.y/kernel/trace/trace.c @@ -2382,11 +2382,19 @@ tracing_write_stub(struct file *filp, co 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, };
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