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Date: Sat, 31 May 2008 20:39:40 -0700 From: Arjan van de Ven <arjan@...radead.org> To: airlied@...ux.ie Cc: linux-kernel@...r.kernel.org Subject: [PATCH] drm: fix crash due to /proc registration race From: Arjan van de Ven <arjan@...ux.intel.com> Subject: [PATCH] drm: fix crash due to /proc registration race The DRM layer creates proc entries like this: ent = create_proc_entry(drm_proc_list[i].name, S_IFREG | S_IRUGO, minor->dev_root); if (!ent) { ... stuff ... } ent->read_proc = drm_proc_list[i].f; ent->data = minor; however that leaves a short window where the /proc file is visible, but where ->data is not initialized yet. It appears that this race is actually hit in practice: http://www.kerneloops.org/search.php?search=drm_name_info (of course it could be some other race.. but this race appears to be there at least) Reported-by: www.kerneloops.org Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com> --- drivers/char/drm/drm_proc.c | 13 ++++++++++++- 1 files changed, 12 insertions(+), 1 deletions(-) diff --git a/drivers/char/drm/drm_proc.c b/drivers/char/drm/drm_proc.c index 93b1e04..19e61ad 100644 --- a/drivers/char/drm/drm_proc.c +++ b/drivers/char/drm/drm_proc.c @@ -164,9 +164,20 @@ static int drm_name_info(char *buf, char **start, off_t offset, int request, int *eof, void *data) { struct drm_minor *minor = (struct drm_minor *) data; - struct drm_device *dev = minor->dev; + struct drm_device *dev; int len = 0; + /* + * When creating the /proc files, there is a tiny race window + * where "data" isn't assigned yet... error out rather than dereference + */ + if (!data) { + *eof = 1; + return 0; + } + + dev = minor->dev; + if (offset > DRM_PROC_LIMIT) { *eof = 1; return 0; -- 1.5.5.1 -- If you want to reach me at my work email, use arjan@...ux.intel.com For development, discussion and tips for power savings, visit http://www.lesswatts.org -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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