Subject: + sysctl-clean-up-char-buffer-arguments.patch added to -mm tree To: keescook@xxxxxxxxxxxx,rdunlap@xxxxxxxxxxxxx From: akpm@xxxxxxxxxxxxxxxxxxxx Date: Mon, 05 May 2014 15:00:25 -0700 The patch titled Subject: sysctl: clean up char buffer arguments has been added to the -mm tree. Its filename is sysctl-clean-up-char-buffer-arguments.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/sysctl-clean-up-char-buffer-arguments.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/sysctl-clean-up-char-buffer-arguments.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Kees Cook <keescook@xxxxxxxxxxxx> Subject: sysctl: clean up char buffer arguments When writing to a sysctl string, each write, regardless of VFS position, began writing the string from the start. This meant the contents of the last write to the sysctl controlled the string contents instead of the first. This misbehavior was featured in an exploit against Chrome OS. While it's not in itself a vulnerability, it's a weirdness that isn't on the mind of most auditors: "This filter looks correct, the first line written would not be meaningful to sysctl" doesn't apply here, since the size of the write and the contents of the final write are what matter when writing to sysctls. This adds the sysctl kernel.sysctl_writes_strict to control the write behavior. The default (0) reports when VFS position is non-0 on a write, but retains legacy behavior, -1 disables the warning, and 1 enables the position-respecting behavior. The long-term plan here is to wait for userspace to be fixed in response to the new warning and to then switch the default kernel behavior to the new position-respecting behavior. This patch (of 4): The char buffer arguments are needlessly cast in weird places. Clean it up so things are easier to read. Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/sysctl.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff -puN kernel/sysctl.c~sysctl-clean-up-char-buffer-arguments kernel/sysctl.c --- a/kernel/sysctl.c~sysctl-clean-up-char-buffer-arguments +++ a/kernel/sysctl.c @@ -1698,8 +1698,8 @@ int __init sysctl_init(void) #ifdef CONFIG_PROC_SYSCTL -static int _proc_do_string(void* data, int maxlen, int write, - void __user *buffer, +static int _proc_do_string(char *data, int maxlen, int write, + char __user *buffer, size_t *lenp, loff_t *ppos) { size_t len; @@ -1725,7 +1725,7 @@ static int _proc_do_string(void* data, i len = maxlen-1; if(copy_from_user(data, buffer, len)) return -EFAULT; - ((char *) data)[len] = 0; + data[len] = 0; *ppos += *lenp; } else { len = strlen(data); @@ -1743,10 +1743,10 @@ static int _proc_do_string(void* data, i if (len > *lenp) len = *lenp; if (len) - if(copy_to_user(buffer, data, len)) + if (copy_to_user(buffer, data, len)) return -EFAULT; if (len < *lenp) { - if(put_user('\n', ((char __user *) buffer) + len)) + if (put_user('\n', buffer + len)) return -EFAULT; len++; } @@ -1776,8 +1776,8 @@ static int _proc_do_string(void* data, i int proc_dostring(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { - return _proc_do_string(table->data, table->maxlen, write, - buffer, lenp, ppos); + return _proc_do_string((char *)(table->data), table->maxlen, write, + (char __user *)buffer, lenp, ppos); } static size_t proc_skip_spaces(char **buf) _ Patches currently in -mm which might be from keescook@xxxxxxxxxxxx are lib-vsprintf-add-%pt-format-specifier.patch binfmt_elfc-use-get_random_int-to-fix-entropy-depleting.patch ptrace-fix-fork-event-messages-across-pid-namespaces.patch sysctl-clean-up-char-buffer-arguments.patch sysctl-refactor-sysctl-string-writing-logic.patch sysctl-allow-for-strict-write-position-handling.patch sysctl-allow-for-strict-write-position-handling-fix.patch tools-testing-selftests-sysctl-validate-sysctl_writes_strict.patch tools-testing-selftests-sysctl-validate-sysctl_writes_strict-fix.patch linux-next.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html