From 5d46f3266728913d05106ee82fb5f043be06eb21 Mon Sep 17 00:00:00 2001 From: Vasiliy Kulikov Date: Thu, 14 Apr 2011 19:56:25 +0400 Subject: [PATCH] staging: istallion: fix arbitrary kernel memory reads/writes stli_brdstats is defined as global variable. After de-BKL-ization in the patch b4eda9cb48eac1b7 an access to the variable is not serialized anymore. This leads to the race window between the check and the use in stli_getbrdstats(): if (copy_from_user(&stli_brdstats, bp, sizeof(combrd_t))) return -EFAULT; if (stli_brdstats.brd >= STL_MAXBRDS) <<< return -ENODEV; brdp = stli_brds[stli_brdstats.brd]; <<< If one process calls COM_GETBRDSTATS ioctl() with sane .brd, second process calls COM_GETBRDSTATS ioctl() with invalid .brd, and the second process' copy_from_user() executes exactly between the check and stli_brds[] indexation of the first process, then the first process gets contents of memory at *stli_brds[stli_brdstats.brd] address. Also the resulting .nrpanels field may be too big, in this case stli_brdstats.panels array overflows. Signed-off-by: Vasiliy Kulikov Signed-off-by: Greg Kroah-Hartman --- drivers/staging/tty/istallion.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/staging/tty/istallion.c b/drivers/staging/tty/istallion.c index 0b266272cccd..ca18cbf4e3c9 100644 --- a/drivers/staging/tty/istallion.c +++ b/drivers/staging/tty/istallion.c @@ -186,7 +186,6 @@ static struct ktermios stli_deftermios = { * re-used for each stats call. */ static comstats_t stli_comstats; -static combrd_t stli_brdstats; static struct asystats stli_cdkstats; /*****************************************************************************/ @@ -4005,6 +4004,7 @@ static int stli_getbrdstats(combrd_t __user *bp) { struct stlibrd *brdp; unsigned int i; + combrd_t stli_brdstats; if (copy_from_user(&stli_brdstats, bp, sizeof(combrd_t))) return -EFAULT; -- 2.20.1