From: Alexey Dobriyan <adobriyan@xxxxxxxxx> Subject: proc: fix /proc/*/map_files lookup 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@xxxxxxxxx> Cc: Pavel Emelyanov <xemul@xxxxxxxxxx> Cc: Andrei Vagin <avagin@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/proc/base.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) diff -puN fs/proc/base.c~proc-fix-proc-map_files-lookup fs/proc/base.c --- a/fs/proc/base.c~proc-fix-proc-map_files-lookup +++ a/fs/proc/base.c @@ -100,6 +100,8 @@ #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 @@ -1906,8 +1908,33 @@ 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; } _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
