[PATCH] i2c: fix stack buffer overflow vulnerability in i2c md command

When running "i2c md 0 0 80000100", the function do_i2c_md parses the
length into an unsigned int variable named length. The value is then
moved to a signed variable:

    int nbytes = length;
    #define DISP_LINE_LEN 16
    int linebytes = (nbytes > DISP_LINE_LEN) ? DISP_LINE_LEN : nbytes;
    ret = dm_i2c_read(dev, addr, linebuf, linebytes);

On systems where integers are 32 bits wide, 0x80000100 is a negative
value to "nbytes > DISP_LINE_LEN" is false and linebytes gets assigned
0x80000100 instead of 16.

The consequence is that the function which reads from the i2c device
(dm_i2c_read or i2c_read) is called with a 16-byte stack buffer to fill
but with a size parameter which is too large. In some cases, this could
trigger a crash. But with some i2c drivers, such as drivers/i2c/nx_i2c.c
(used with "nexell,s5pxx18-i2c" bus), the size is actually truncated to
a 16-bit integer. This is because function i2c_transfer expects an
unsigned short length. In such a case, an attacker who can control the
response of an i2c device can overwrite the return address of a function
and execute arbitrary code through Return-Oriented Programming.

Fix this issue by using unsigned integers types in do_i2c_md. While at
it, make also alen unsigned, as signed sizes can cause vulnerabilities
when people forgot to check that they can be negative.

Signed-off-by: Nicolas Iooss <nicolas.iooss+uboot@ledger.fr>
Reviewed-by: Heiko Schocher <hs@denx.de>
Reviewed-By: Daniel Leidert <dleidert@debian.org>
Origin: https://source.denx.de/u-boot/u-boot/-/commit/8f8c04bf1ebbd2f72f1643e7ad9617dafa6e5409
Bug: https://lists.denx.de/pipermail/u-boot/2022-June/486113.html
Bug-Debian: https://bugs.debian.org/1014529
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2022-34835
Bug-Freexian-Security: https://deb.freexian.com/extended-lts/tracker/CVE-2022-34835

Gbp-Pq: Name CVE-2022-34835.patch

diff --git a/cmd/i2c.c b/cmd/i2c.c
index cc01119b2107381d05577a1233c4d3f24e087d33..6135fb2295845b80d7f1516141bed86f52bbb4ff 100644 (file)
--- a/cmd/i2c.c
+++ b/cmd/i2c.c
@@ -248,10 +248,10 @@ int i2c_set_bus_speed(unsigned int speed)
  *
  * Returns the address length.
  */
-static uint get_alen(char *arg, int default_len)
+static uint get_alen(char *arg, uint default_len)
 {
-       int     j;
-       int     alen;
+       uint    j;
+       uint    alen;
 
        alen = default_len;
        for (j = 0; j < 8; j++) {
@@ -295,7 +295,7 @@ static int do_i2c_read(struct cmd_tbl *cmdtp, int flag, int argc,
 {
        uint    chip;
        uint    devaddr, length;
-       int alen;
+       uint    alen;
        u_char  *memaddr;
        int ret;
 #ifdef CONFIG_DM_I2C
@@ -349,7 +349,7 @@ static int do_i2c_write(struct cmd_tbl *cmdtp, int flag, int argc,
 {
        uint    chip;
        uint    devaddr, length;
-       int alen;
+       uint    alen;
        u_char  *memaddr;
        int ret;
 #ifdef CONFIG_DM_I2C
@@ -517,8 +517,8 @@ static int do_i2c_md(struct cmd_tbl *cmdtp, int flag, int argc,
 {
        uint    chip;
        uint    addr, length;
-       int alen;
-       int     j, nbytes, linebytes;
+       uint    alen;
+       uint    j, nbytes, linebytes;
        int ret;
 #ifdef CONFIG_DM_I2C
        struct udevice *dev;
@@ -637,9 +637,9 @@ static int do_i2c_mw(struct cmd_tbl *cmdtp, int flag, int argc,
 {
        uint    chip;
        ulong   addr;
-       int     alen;
+       uint    alen;
        uchar   byte;
-       int     count;
+       uint    count;
        int ret;
 #ifdef CONFIG_DM_I2C
        struct udevice *dev;
@@ -724,8 +724,8 @@ static int do_i2c_crc(struct cmd_tbl *cmdtp, int flag, int argc,
 {
        uint    chip;
        ulong   addr;
-       int     alen;
-       int     count;
+       uint    alen;
+       uint    count;
        uchar   byte;
        ulong   crc;
        ulong   err;
@@ -1033,7 +1033,7 @@ static int do_i2c_loop(struct cmd_tbl *cmdtp, int flag, int argc,
                       char *const argv[])
 {
        uint    chip;
-       int alen;
+       uint    alen;
        uint    addr;
        uint    length;
        u_char  bytes[16];