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authorKees Cook <keescook@chromium.org>2014-06-06 14:37:18 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-06 16:08:13 -0700
commit2ca9bb456ada8bcbdc8f77f8fc78207653bbaa92 (patch)
tree05f8bd09ad6e9b24b735d7cf90c3167bade83050 /kernel/sysctl.c
parentf88083005ab319abba5d0b2e4e997558245493c8 (diff)
downloadlinux-sh-2ca9bb456ada8bcbdc8f77f8fc78207653bbaa92.tar.gz
sysctl: refactor sysctl string writing logic
Consolidate buffer length checking with new-line/end-of-line checking. Additionally, instead of reading user memory twice, just do the assignment during the loop. This change doesn't affect the potential races here. It was already possible to read a sysctl that was in the middle of a write. In both cases, the string will always be NULL terminated. The pre-existing race remains a problem to be solved. Signed-off-by: Kees Cook <keescook@chromium.org> Cc: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/sysctl.c')
-rw-r--r--kernel/sysctl.c11
1 files changed, 4 insertions, 7 deletions
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 3e214beabbe9..ac6847feaa83 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1717,21 +1717,18 @@ static int _proc_do_string(char *data, int maxlen, int write,
}
if (write) {
+ /* Start writing from beginning of buffer. */
len = 0;
+ *ppos += *lenp;
p = buffer;
- while (len < *lenp) {
+ while ((p - buffer) < *lenp && len < maxlen - 1) {
if (get_user(c, p++))
return -EFAULT;
if (c == 0 || c == '\n')
break;
- len++;
+ data[len++] = c;
}
- if (len >= maxlen)
- len = maxlen-1;
- if(copy_from_user(data, buffer, len))
- return -EFAULT;
data[len] = 0;
- *ppos += *lenp;
} else {
len = strlen(data);
if (len > maxlen)