From 4909724b5dee8fb7c52bbe90afa40c65b17be9eb Mon Sep 17 00:00:00 2001 From: Alexandra Kossovsky Date: Sun, 20 Nov 2005 13:41:59 -0800 Subject: [PATCH] [COMPAT] net: SIOCGIFCONF data corruption From: Alexandra Kossovsky From http://bugzilla.kernel.org/show_bug.cgi?id=4746 There is user data corruption when using ioctl(SIOCGIFCONF) in 32-bit application running amd64 kernel. I do not think that this problem is exploitable, but any data corruption may lead to security problems. Following code demonstrates the problem #include #include #include #include #include #include char buf[256]; main() { int s = socket(AF_INET, SOCK_DGRAM, 0); struct ifconf req; int i; req.ifc_buf = buf; req.ifc_len = 41; printf("Result %d\n", ioctl(s, SIOCGIFCONF, &req)); printf("Len %d\n", req.ifc_len); for (i = 41; i < 256; i++) if (buf[i] != 0) printf("Byte %d is corrupted\n", i); } Steps to reproduce: Compile the code above into 32-bit elf and run it. You'll get Result 0 Len 32 Byte 48 is corrupted Byte 52 is corrupted Byte 53 is corrupted Byte 54 is corrupted Byte 55 is corrupted Signed-off-by: Andrew Morton Signed-off-by: David S. Miller --- fs/compat_ioctl.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/fs/compat_ioctl.c b/fs/compat_ioctl.c index 31b7efd94d66..43a2508ac696 100644 --- a/fs/compat_ioctl.c +++ b/fs/compat_ioctl.c @@ -686,7 +686,8 @@ static int dev_ifconf(unsigned int fd, unsigned int cmd, unsigned long arg) ifr = ifc.ifc_req; ifr32 = compat_ptr(ifc32.ifcbuf); - for (i = 0, j = 0; i < ifc32.ifc_len && j < ifc.ifc_len; + for (i = 0, j = 0; + i + sizeof (struct ifreq32) < ifc32.ifc_len && j < ifc.ifc_len; i += sizeof (struct ifreq32), j += sizeof (struct ifreq)) { if (copy_in_user(ifr32, ifr, sizeof (struct ifreq32))) return -EFAULT; @@ -702,10 +703,7 @@ static int dev_ifconf(unsigned int fd, unsigned int cmd, unsigned long arg) i = ((i / sizeof(struct ifreq)) * sizeof(struct ifreq32)); ifc32.ifc_len = i; } else { - if (i <= ifc32.ifc_len) - ifc32.ifc_len = i; - else - ifc32.ifc_len = i - sizeof (struct ifreq32); + ifc32.ifc_len = i; } if (copy_to_user(compat_ptr(arg), &ifc32, sizeof(struct ifconf32))) return -EFAULT; -- 2.30.2