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-rw-r--r--fs/proc/base.c28
1 files changed, 23 insertions, 5 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index b6572944efc3..aaffc0c30216 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -235,6 +235,10 @@ static ssize_t get_mm_cmdline(struct mm_struct *mm, char __user *buf,
if (env_start != arg_end || env_start >= env_end)
env_start = env_end = arg_end;
+ /* .. and limit it to a maximum of one page of slop */
+ if (env_end >= arg_end + PAGE_SIZE)
+ env_end = arg_end + PAGE_SIZE - 1;
+
/* We're not going to care if "*ppos" has high bits set */
pos = arg_start + *ppos;
@@ -254,10 +258,19 @@ static ssize_t get_mm_cmdline(struct mm_struct *mm, char __user *buf,
while (count) {
int got;
size_t size = min_t(size_t, PAGE_SIZE, count);
+ long offset;
- got = access_remote_vm(mm, pos, page, size, FOLL_ANON);
- if (got <= 0)
+ /*
+ * Are we already starting past the official end?
+ * We always include the last byte that is *supposed*
+ * to be NUL
+ */
+ offset = (pos >= arg_end) ? pos - arg_end + 1 : 0;
+
+ got = access_remote_vm(mm, pos - offset, page, size + offset, FOLL_ANON);
+ if (got <= offset)
break;
+ got -= offset;
/* Don't walk past a NUL character once you hit arg_end */
if (pos + got >= arg_end) {
@@ -276,12 +289,17 @@ static ssize_t get_mm_cmdline(struct mm_struct *mm, char __user *buf,
n = arg_end - pos - 1;
/* Cut off at first NUL after 'n' */
- got = n + strnlen(page+n, got-n);
- if (!got)
+ got = n + strnlen(page+n, offset+got-n);
+ if (got < offset)
break;
+ got -= offset;
+
+ /* Include the NUL if it existed */
+ if (got < size)
+ got++;
}
- got -= copy_to_user(buf, page, got);
+ got -= copy_to_user(buf, page+offset, got);
if (unlikely(!got)) {
if (!len)
len = -EFAULT;