On Mon, Oct 07, 2024 at 05:57:18PM +0900, Jeongjun Park wrote:
Greg KH gregkh@linuxfoundation.org wrote:
On Mon, Oct 07, 2024 at 03:53:07PM +0900, Jeongjun Park wrote:
Looking at the source code links for mm/memory.c in the sample reports in the syzbot report links [1].
it looks like the line numbers are designated as lines that have been increased by 1. This may seem like a problem with syzkaller or the addr2line program that assigns the line numbers, but there is no problem with either of them.
In the previous commit d61ea1cb0095 ("userfaultfd: UFFD_FEATURE_WP_ASYNC"), when modifying mm/memory.c, an unknown line break is added to the very first line of the file. However, the git.kernel.org site displays the source code with the added line break removed, so even though addr2line has assigned the correct line number, it looks like the line number has increased by 1.
This may seem like a trivial thing, but I think it would be appropriate to remove all the newline characters added to the upstream and stable versions, as they are not only incorrect in terms of code style but also hinder bug analysis.
[1]
https://syzkaller.appspot.com/bug?extid=4145b11cdf925264bff4 https://syzkaller.appspot.com/bug?extid=fa43f1b63e3aa6f66329 https://syzkaller.appspot.com/bug?extid=890a1df7294175947697
Fixes: d61ea1cb0095 ("userfaultfd: UFFD_FEATURE_WP_ASYNC") Cc: stable@vger.kernel.org Signed-off-by: Jeongjun Park aha310510@gmail.com
mm/memory.c | 1 - 1 file changed, 1 deletion(-)
diff --git a/mm/memory.c b/mm/memory.c index 2366578015ad..7dffe8749014 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1,4 +1,3 @@
This sounds like you have broken tools that can not handle an empty line in a file.
Why not fix those?
As I mentioned above, there is no problem with addr2line's ability to parse the code line that called the function in the calltrace of the crash report.
However, when the source code of mm/memory.c is printed on the screen on the git.kernel.org site, the line break character that exists in the first line of the file is deleted and printed, so as a result, all code lines in the mm/memory.c file are located at line numbers that are -1 less than the actual line.
You can understand it easily if you compare the source code of mm/memory.c on github and git.kernel.org.
https://github.com/torvalds/linux/blob/master/mm/memory.c https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/m...
Since I cannot modify the source code printing function of the git.kernel.org site, the best solution I can suggest is to remove the unnecessary line break character that exists in all versions.
I would recommend fixing the git.kernel.org code, it is all open source and can be fixed up, as odds are other projects/repos would like to have it fixed as well.
thanks,
greg k-h