From fb910c42ccebf853c29296185c45c11164a56098 Mon Sep 17 00:00:00 2001 From: Joe Lawrence Date: Fri, 17 Nov 2017 15:29:28 -0800 Subject: sysctl: check for UINT_MAX before unsigned int min/max Mikulas noticed in the existing do_proc_douintvec_minmax_conv() and do_proc_dopipe_max_size_conv() introduced in this patchset, that they inconsistently handle overflow and min/max range inputs: For example: 0 ... param->min - 1 ---> ERANGE param->min ... param->max ---> the value is accepted param->max + 1 ... 0x100000000L + param->min - 1 ---> ERANGE 0x100000000L + param->min ... 0x100000000L + param->max ---> EINVAL 0x100000000L + param->max + 1, 0x200000000L + param->min - 1 ---> ERANGE 0x200000000L + param->min ... 0x200000000L + param->max ---> EINVAL 0x200000000L + param->max + 1, 0x300000000L + param->min - 1 ---> ERANGE In do_proc_do*() routines which store values into unsigned int variables (4 bytes wide for 64-bit builds), first validate that the input unsigned long value (8 bytes wide for 64-bit builds) will fit inside the smaller unsigned int variable. Then check that the unsigned int value falls inside the specified parameter min, max range. Otherwise the unsigned long -> unsigned int conversion drops leading bits from the input value, leading to the inconsistent pattern Mikulas documented above. Link: http://lkml.kernel.org/r/1507658689-11669-5-git-send-email-joe.lawrence@redhat.com Signed-off-by: Joe Lawrence Reported-by: Mikulas Patocka Reviewed-by: Mikulas Patocka Cc: Al Viro Cc: Jens Axboe Cc: Michael Kerrisk Cc: Randy Dunlap Cc: Josh Poimboeuf Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/sysctl.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) (limited to 'kernel/sysctl.c') diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 138b6484f277..dd25d90896fc 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -2576,12 +2576,13 @@ static int do_proc_douintvec_minmax_conv(unsigned long *lvalp, if (write) { unsigned int val = *lvalp; + if (*lvalp > UINT_MAX) + return -EINVAL; + if ((param->min && *param->min > val) || (param->max && *param->max < val)) return -ERANGE; - if (*lvalp > UINT_MAX) - return -EINVAL; *valp = val; } else { unsigned int val = *valp; @@ -2632,17 +2633,18 @@ static int do_proc_dopipe_max_size_conv(unsigned long *lvalp, struct do_proc_dopipe_max_size_conv_param *param = data; if (write) { - unsigned int val = round_pipe_size(*lvalp); + unsigned int val; + if (*lvalp > UINT_MAX) + return -EINVAL; + + val = round_pipe_size(*lvalp); if (val == 0) return -EINVAL; if (param->min && *param->min > val) return -ERANGE; - if (*lvalp > UINT_MAX) - return -EINVAL; - *valp = val; } else { unsigned int val = *valp; -- cgit v1.2.3-59-g8ed1b