4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Alexey Dobriyan adobriyan@gmail.com
[ Upstream commit ac7f1061c2c11bb8936b1b6a94cdb48de732f7a4 ]
Current code does:
if (sscanf(dentry->d_name.name, "%lx-%lx", start, end) != 2)
However sscanf() is broken garbage.
It silently accepts whitespace between format specifiers (did you know that?).
It silently accepts valid strings which result in integer overflow.
Do not use sscanf() for any even remotely reliable parsing code.
OK # readlink '/proc/1/map_files/55a23af39000-55a23b05b000' /lib/systemd/systemd
broken # readlink '/proc/1/map_files/ 55a23af39000-55a23b05b000' /lib/systemd/systemd
broken # readlink '/proc/1/map_files/55a23af39000-55a23b05b000 ' /lib/systemd/systemd
very broken # readlink '/proc/1/map_files/1000000000000000055a23af39000-55a23b05b000' /lib/systemd/systemd
Andrei said:
: This patch breaks criu. It was a bug in criu. And this bug is on a minor : path, which works when memfd_create() isn't available. It is a reason why : I ask to not backport this patch to stable kernels. : : In CRIU this bug can be triggered, only if this patch will be backported : to a kernel which version is lower than v3.16.
Link: http://lkml.kernel.org/r/20171120212706.GA14325@avx2 Signed-off-by: Alexey Dobriyan adobriyan@gmail.com Cc: Pavel Emelyanov xemul@openvz.org Cc: Andrei Vagin avagin@virtuozzo.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/proc/base.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-)
--- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -94,6 +94,8 @@ #include "internal.h" #include "fd.h"
+#include "../../lib/kstrtox.h" + /* NOTE: * Implementing inode permission operations in /proc is almost * certainly an error. Permission checks need to happen during @@ -1864,8 +1866,33 @@ end_instantiate: static int dname_to_vma_addr(struct dentry *dentry, unsigned long *start, unsigned long *end) { - if (sscanf(dentry->d_name.name, "%lx-%lx", start, end) != 2) + const char *str = dentry->d_name.name; + unsigned long long sval, eval; + unsigned int len; + + len = _parse_integer(str, 16, &sval); + if (len & KSTRTOX_OVERFLOW) + return -EINVAL; + if (sval != (unsigned long)sval) return -EINVAL; + str += len; + + if (*str != '-') + return -EINVAL; + str++; + + len = _parse_integer(str, 16, &eval); + if (len & KSTRTOX_OVERFLOW) + return -EINVAL; + if (eval != (unsigned long)eval) + return -EINVAL; + str += len; + + if (*str != '\0') + return -EINVAL; + + *start = sval; + *end = eval;
return 0; }