lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Date:   Wed, 24 Feb 2021 17:02:09 -0800
From:   Ivan Babrou <>
To:     kernel-team <>
Cc:     "Matthew Wilcox (Oracle)" <>,
        Christoph Hellwig <>,
        Al Viro <>,
        Luis Chamberlain <>,
        Kees Cook <>,
        Iurii Zaikin <>,
        Alexey Dobriyan <>,
        linux-kernel <>,
Subject: Memory allocation issues after "sysctl: Convert to iter interfaces"


We started seeing allocation failures on procfs reads after
commit 4bd6a7353ee1 "sysctl: Convert to iter interfaces".

I haven't done a full bisect, but the decoded stacks point
squarely at the following piece of code which was introduced:

kbuf = kzalloc(count + 1, GFP_KERNEL);

Previously reading /proc/sys/net/core/somaxconn required order 1
and order 3 allocations from the kernel, which can be seen from:

$ sudo perf record -g -e kmem:mm_page_alloc_zone_locked -- \
    cat /proc/sys/net/core/somaxconn

Now we see order 6 + order 6 allocations from cat, and even:

read(3, 0x7f8d9d3f3000, 131072) = -1 ENOMEM (Cannot allocate memory)

See the following gist for full allocation stacks on 5.4 and 5.10:


This seems like a regression, and unprivileged users being
able to force order 6 allocations onto the kernel doesn't feel good.

Powered by blists - more mailing lists