Re: [Qemu-devel] [PATCH] block: Prevent coroutine stack overflow when recursing in bdrv_open_backing_file.

[Kevin Wolf]

[ Cc: qemu-devel ]

Patches should never be sent to qemu-stable only.

Am 23.04.2014 um 13:45 hat Stefan Hajnoczi geschrieben:
> On Tue, Apr 22, 2014 at 05:05:27PM +0200, Benoît Canet wrote:
> > In 1.7.1 qcow2_create2 reopen the file for flushing without the 
> > BDRV_O_NO_BACKING
> > flags.
> > 
> > As a consequence the code would recursively open the whole backing chain.
> > 
> > These three stack arrays would pile up through the recursion and lead to a 
> > coroutine
> > stack overflow.
> > 
> > Convert these array to malloced buffers in order to streamline the coroutine
> > footprint.
> > 
> > Symptoms where freezes or segfaults on production machines while taking QMP 
> > externals
> > snapshots. The overflow disturbed coroutine switching.
> > 
> > Signed-off-by: Benoit Canet <address@hidden>
> > ---
> >  block.c |   32 +++++++++++++++++++-------------
> >  1 file changed, 19 insertions(+), 13 deletions(-)
> 
> This is patch hints at dropping the PATH_MAX constant completely: Let's
> use g_strdup()/g_strdup_printf()/etc for filenames and stop using
> hard-coded limits.  But as a bug fix this patch is good.
> 
> I had to resolve conflicts against the block tree - I guess you wrote
> the patch against v1.7.1.
> 
> Thanks, applied to my block tree:
> https://github.com/stefanha/qemu/commits/block
> 
> Stefan