From: Waiman Long <longman@xxxxxxxxxx> Subject: ipc: IPCMNI limit check for msgmni and shmmni Patch series "ipc: IPCMNI limit check for *mni & increase that limit", v9. The sysctl parameters msgmni, shmmni and semmni have an inherent limit of IPC_MNI (32k). However, users may not be aware of that because they can write a value much higher than that without getting any error or notification. Reading the parameters back will show the newly written values which are not real. The real IPCMNI limit is now enforced to make sure that users won't put in an unrealistic value. The first 2 patches enforce the limits. There are also users out there requesting increase in the IPCMNI value. The last 2 patches attempt to do that by using a boot kernel parameter "ipcmni_extend" to increase the IPCMNI limit from 32k to 8M if the users really want the extended value. This patch (of 4): A user can write arbitrary integer values to msgmni and shmmni sysctl parameters without getting error, but the actual limit is really IPCMNI (32k). This can mislead users as they think they can get a value that is not real. The right limits are now set for msgmni and shmmni so that the users will become aware if they set a value outside of the acceptable range. Link: http://lkml.kernel.org/r/1536352137-12003-2-git-send-email-longman@xxxxxxxxxx Signed-off-by: Waiman Long <longman@xxxxxxxxxx> Acked-by: Luis R. Rodriguez <mcgrof@xxxxxxxxxx> Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> Cc: Takashi Iwai <tiwai@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- ipc/ipc_sysctl.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) --- a/ipc/ipc_sysctl.c~ipc-ipcmni-limit-check-for-msgmni-and-shmmni +++ a/ipc/ipc_sysctl.c @@ -99,6 +99,7 @@ static int proc_ipc_auto_msgmni(struct c static int zero; static int one = 1; static int int_max = INT_MAX; +static int ipc_mni = IPCMNI; static struct ctl_table ipc_kern_table[] = { { @@ -120,7 +121,9 @@ static struct ctl_table ipc_kern_table[] .data = &init_ipc_ns.shm_ctlmni, .maxlen = sizeof(init_ipc_ns.shm_ctlmni), .mode = 0644, - .proc_handler = proc_ipc_dointvec, + .proc_handler = proc_ipc_dointvec_minmax, + .extra1 = &zero, + .extra2 = &ipc_mni, }, { .procname = "shm_rmid_forced", @@ -147,7 +150,7 @@ static struct ctl_table ipc_kern_table[] .mode = 0644, .proc_handler = proc_ipc_dointvec_minmax, .extra1 = &zero, - .extra2 = &int_max, + .extra2 = &ipc_mni, }, { .procname = "auto_msgmni", _
