5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Bradley Morgan <redacted>
commit 1f58a5335cdd14b3fb5f2a5d3763dee1f5cba1d3 upstream.
parse() hands nla_strscpy() len as dstsize, and nla_strscpy() copies at
most dstsize - 1 bytes. When the attr payload comes in without a trailing
NUL, srclen == len >= dstsize and the last character of the cpumask string
gets cut off. Register "0-15" and you are silently listening on "0-1",
exit data for the rest never shows up.
The bug only bites when the sender doesn't NUL terminate the payload;
senders that include the NUL were always fine (srclen gets decremented for
the trailing NUL, so srclen < dstsize). Thats probably why this survived
20 years. And the policy is NLA_STRING, not NLA_NUL_STRING, so a payload
without the trailing NUL is legit input here.
Skip the kmalloc/nla_strscpy dance entirely and use nla_strdup(), which
already allocates srclen + 1 and terminates. The nla_len() bounds checks
stay as they were.
Link: https://lore.kernel.org/EC49FE41-7F5F-41E0-A07A-ABEB8ECA514D@grrlz.net (local)
Fixes: f9fd8914c1ac ("[PATCH] per-task delay accounting taskstats interface: control exit data through cpumasks")
Signed-off-by: Bradley Morgan <redacted>
Reported-by: Oleg Deomi <redacted>
Closes: https://lore.kernel.org/CAByWkfZ6b1=3H9pwkz-dDQOs9cZaF-HYQ6b9Yb0=Hq2r1Vv_Pw@mail.gmail.com (local)
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: <redacted>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/taskstats.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -346,10 +346,9 @@ static int parse(struct nlattr *na, stru
return -E2BIG;
if (len < 1)
return -EINVAL;
- data = kmalloc(len, GFP_KERNEL);
+ data = nla_strdup(na, GFP_KERNEL);
if (!data)
return -ENOMEM;
- nla_strscpy(data, na, len);
ret = cpulist_parse(data, mask);
kfree(data);
return ret;