From: Pavel Skripkin <paskripkin@xxxxxxxxx> Subject: profiling: fix shift-out-of-bounds bugs Syzbot reported shift-out-of-bounds bug in profile_init(). The problem was in incorrect prof_shift. Since prof_shift value comes from userspace we need to clamp this value into [0, BITS_PER_LONG -1] boundaries. Second possible shiht-out-of-bounds was found by Tetsuo: sample_step local variable in read_profile() had "unsigned int" type, but prof_shift allows to make a BITS_PER_LONG shift. So, to prevent possible shiht-out-of-bounds sample_step type was changed to "unsigned long". Also, "unsigned short int" will be sufficient for storing [0, BITS_PER_LONG] value, that's why there is no need for "unsigned long" prof_shift. Link: https://lkml.kernel.org/r/20210813140022.5011-1-paskripkin@xxxxxxxxx Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-and-tested-by: syzbot+e68c89a9510c159d9684@xxxxxxxxxxxxxxxxxxxxxxxxx Suggested-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Pavel Skripkin <paskripkin@xxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/profile.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) --- a/kernel/profile.c~profiling-fix-shift-out-of-bounds-bugs +++ a/kernel/profile.c @@ -41,7 +41,8 @@ struct profile_hit { #define NR_PROFILE_GRP (NR_PROFILE_HIT/PROFILE_GRPSZ) static atomic_t *prof_buffer; -static unsigned long prof_len, prof_shift; +static unsigned long prof_len; +static unsigned short int prof_shift; int prof_on __read_mostly; EXPORT_SYMBOL_GPL(prof_on); @@ -67,8 +68,8 @@ int profile_setup(char *str) if (str[strlen(sleepstr)] == ',') str += strlen(sleepstr) + 1; if (get_option(&str, &par)) - prof_shift = par; - pr_info("kernel sleep profiling enabled (shift: %ld)\n", + prof_shift = clamp(par, 0, BITS_PER_LONG - 1); + pr_info("kernel sleep profiling enabled (shift: %u)\n", prof_shift); #else pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n"); @@ -78,21 +79,21 @@ int profile_setup(char *str) if (str[strlen(schedstr)] == ',') str += strlen(schedstr) + 1; if (get_option(&str, &par)) - prof_shift = par; - pr_info("kernel schedule profiling enabled (shift: %ld)\n", + prof_shift = clamp(par, 0, BITS_PER_LONG - 1); + pr_info("kernel schedule profiling enabled (shift: %u)\n", prof_shift); } else if (!strncmp(str, kvmstr, strlen(kvmstr))) { prof_on = KVM_PROFILING; if (str[strlen(kvmstr)] == ',') str += strlen(kvmstr) + 1; if (get_option(&str, &par)) - prof_shift = par; - pr_info("kernel KVM profiling enabled (shift: %ld)\n", + prof_shift = clamp(par, 0, BITS_PER_LONG - 1); + pr_info("kernel KVM profiling enabled (shift: %u)\n", prof_shift); } else if (get_option(&str, &par)) { - prof_shift = par; + prof_shift = clamp(par, 0, BITS_PER_LONG - 1); prof_on = CPU_PROFILING; - pr_info("kernel profiling enabled (shift: %ld)\n", + pr_info("kernel profiling enabled (shift: %u)\n", prof_shift); } return 1; @@ -468,7 +469,7 @@ read_profile(struct file *file, char __u unsigned long p = *ppos; ssize_t read; char *pnt; - unsigned int sample_step = 1 << prof_shift; + unsigned long sample_step = 1UL << prof_shift; profile_flip_buffers(); if (p >= (prof_len+1)*sizeof(unsigned int)) _
