From: Waiman Long <longman@xxxxxxxxxx> Subject: ipc: IPCMNI limit check for semmni For SysV semaphores, the semmni value is the last part of the 4-element sem number array. To make semmni behave in a similar way to msgmni and shmmni, we can't directly use the _minmax handler. Instead, a special sem specific handler is added to check the last argument to make sure that it is limited to the [0, IPCMNI] range. An error will be returned if this is not the case. Link: http://lkml.kernel.org/r/1536352137-12003-3-git-send-email-longman@xxxxxxxxxx Signed-off-by: Waiman Long <longman@xxxxxxxxxx> Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx> Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Luis R. Rodriguez <mcgrof@xxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Takashi Iwai <tiwai@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- ipc/ipc_sysctl.c | 23 ++++++++++++++++++++++- ipc/util.h | 9 +++++++++ 2 files changed, 31 insertions(+), 1 deletion(-) --- a/ipc/ipc_sysctl.c~ipc-ipcmni-limit-check-for-semmni +++ a/ipc/ipc_sysctl.c @@ -88,12 +88,33 @@ static int proc_ipc_auto_msgmni(struct c return proc_dointvec_minmax(&ipc_table, write, buffer, lenp, ppos); } +static int proc_ipc_sem_dointvec(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, loff_t *ppos) +{ + int ret, semmni; + struct ipc_namespace *ns = current->nsproxy->ipc_ns; + + semmni = ns->sem_ctls[3]; + ret = proc_ipc_dointvec(table, write, buffer, lenp, ppos); + + if (!ret) + ret = sem_check_semmni(current->nsproxy->ipc_ns); + + /* + * Reset the semmni value if an error happens. + */ + if (ret) + ns->sem_ctls[3] = semmni; + return ret; +} + #else #define proc_ipc_doulongvec_minmax NULL #define proc_ipc_dointvec NULL #define proc_ipc_dointvec_minmax NULL #define proc_ipc_dointvec_minmax_orphans NULL #define proc_ipc_auto_msgmni NULL +#define proc_ipc_sem_dointvec NULL #endif static int zero; @@ -175,7 +196,7 @@ static struct ctl_table ipc_kern_table[] .data = &init_ipc_ns.sem_ctls, .maxlen = 4*sizeof(int), .mode = 0644, - .proc_handler = proc_ipc_dointvec, + .proc_handler = proc_ipc_sem_dointvec, }, #ifdef CONFIG_CHECKPOINT_RESTORE { --- a/ipc/util.h~ipc-ipcmni-limit-check-for-semmni +++ a/ipc/util.h @@ -217,6 +217,15 @@ int ipcget(struct ipc_namespace *ns, str void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids, void (*free)(struct ipc_namespace *, struct kern_ipc_perm *)); +static inline int sem_check_semmni(struct ipc_namespace *ns) { + /* + * Check semmni range [0, IPCMNI] + * semmni is the last element of sem_ctls[4] array + */ + return ((ns->sem_ctls[3] < 0) || (ns->sem_ctls[3] > IPCMNI)) + ? -ERANGE : 0; +} + #ifdef CONFIG_COMPAT #include <linux/compat.h> struct compat_ipc_perm { _
