Re: [PATCH v2 3/3] kexec: Introduce paramters load_limit_reboot and load_limit_panic
Hi Joel Thanks for looking into this On Thu, 15 Dec 2022 at 20:16, Joel Fernandes wrote: > > Hi Ricardo, > > On Thu, Dec 08, 2022 at 05:38:02PM +0100, Ricardo Ribalda wrote: > > Add two parameter to specify how many times a kexec kernel can be loaded. > > > > The sysadmin can set different limits for kexec panic and kexec reboot > > kernels. > > > > The value can be modified at runtime via sysfs, but only with a value > > smaller than the current one (except -1). > > > > Signed-off-by: Ricardo Ribalda > > --- > > Documentation/admin-guide/kernel-parameters.txt | 14 > > include/linux/kexec.h | 2 +- > > kernel/kexec.c | 2 +- > > kernel/kexec_core.c | 91 > > - > > kernel/kexec_file.c | 2 +- > > 5 files changed, 106 insertions(+), 5 deletions(-) > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt > > b/Documentation/admin-guide/kernel-parameters.txt > > index 42af9ca0127e..2b37d6a20747 100644 > > --- a/Documentation/admin-guide/kernel-parameters.txt > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > @@ -2374,6 +2374,20 @@ > > for Movable pages. "nn[KMGTPE]", "nn%", and "mirror" > > are exclusive, so you cannot specify multiple forms. > > > > + kexec_core.load_limit_reboot= > > + kexec_core.load_limit_panic= > > + [KNL] > > + This parameter specifies a limit to the number of > > times > > + a kexec kernel can be loaded. > > + Format: > > + -1 = Unlimited. > > + int = Number of times kexec can be called. > > + > > + During runtime, this parameter can be modified with a > > + value smaller than the current one (but not -1). > > + > > + Default: -1 > > + > > kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. > > Format: [,poll interval] > > The controller # is the number of the ehci usb debug > > diff --git a/include/linux/kexec.h b/include/linux/kexec.h > > index e9e1ab5e8006..3d7d10f7187a 100644 > > --- a/include/linux/kexec.h > > +++ b/include/linux/kexec.h > > @@ -407,7 +407,7 @@ extern int kimage_crash_copy_vmcoreinfo(struct kimage > > *image); > > extern struct kimage *kexec_image; > > extern struct kimage *kexec_crash_image; > > > > -bool kexec_load_permited(void); > > +bool kexec_load_permited(bool crash_image); > > > > #ifndef kexec_flush_icache_page > > #define kexec_flush_icache_page(page) > > diff --git a/kernel/kexec.c b/kernel/kexec.c > > index d83fc9093aff..2b0856e83fe1 100644 > > --- a/kernel/kexec.c > > +++ b/kernel/kexec.c > > @@ -193,7 +193,7 @@ static inline int kexec_load_check(unsigned long > > nr_segments, > > int result; > > > > /* We only trust the superuser with rebooting the system. */ > > - if (!kexec_load_permited()) > > + if (!kexec_load_permited(flags & KEXEC_ON_CRASH)) > > nit: permitted. > > > return -EPERM; > > > > /* Permit LSMs and IMA to fail the kexec */ > > diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c > > index 18bd90ca9c99..7f9d5288b24b 100644 > > --- a/kernel/kexec_core.c > > +++ b/kernel/kexec_core.c > > @@ -952,13 +952,100 @@ static int __init kexec_core_sysctl_init(void) > > late_initcall(kexec_core_sysctl_init); > > #endif > > > > -bool kexec_load_permited(void) > > +struct kexec_load_limit { > > + /* Mutex protects the limit count. */ > > + struct mutex mutex; > > + int limit; > > Can you not just use atomic ops for limit, and get rid of the mutex? > > That will simplify the code as well. I could not find a way to use atomic_t. The operations are not just counters, but maybe I am missing a better way to do it :) The current operations: - permitted(): if (param==-1) { return -1; } if (param =0) return -1; param = param -1; - paramter_set() new_param = min(-1, new_param); if (param == -1) { param = new_param; return } if (new_param == -1) { return -EINVAL; } param = min(new_param, param); > > > +}; > > + > > +struct kexec_load_limit load_limit_reboot = { > > + .mutex = __MUTEX_INITIALIZER(load_limit_reboot.mutex), > > + .limit = -1, > > +}; > > + > > +struct kexec_load_limit load_limit_panic = { > > + .mutex = __MUTEX_INITIALIZER(load_limit_panic.mutex), > > + .limit = -1, > > +}; > > + > > +static int param_get_limit(char *buffer, const struct kernel_param *kp) > > { > > + int ret; > > + struct kexec_load_limit *limit = kp->arg; > > + > > + mutex_lock(>mutex); > > + ret = scnprintf(buffer, PAGE_SIZE, "%i\n", limit->limit); > > + mutex_unlock(>mutex); > > + > > + return ret; > > +} > > + > > +static int param_set_limit(const char *buffer, const struct kernel_param >
Re: [PATCH v2 3/3] kexec: Introduce paramters load_limit_reboot and load_limit_panic
On 08/12/2022 13:38, Ricardo Ribalda wrote: > Add two parameter to specify how many times a kexec kernel can be loaded. > > The sysadmin can set different limits for kexec panic and kexec reboot > kernels. > > The value can be modified at runtime via sysfs, but only with a value > smaller than the current one (except -1). > > Signed-off-by: Ricardo Ribalda > --- Thanks for your patches Ricardo! Small nit in the subject: s/paramters/parameters. Just observed that after Joel's review anyway, so kudos to him heh Cheers, Guilherme ___ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
Re: [PATCH v2 3/3] kexec: Introduce paramters load_limit_reboot and load_limit_panic
Hi Ricardo, On Thu, Dec 08, 2022 at 05:38:02PM +0100, Ricardo Ribalda wrote: > Add two parameter to specify how many times a kexec kernel can be loaded. > > The sysadmin can set different limits for kexec panic and kexec reboot > kernels. > > The value can be modified at runtime via sysfs, but only with a value > smaller than the current one (except -1). > > Signed-off-by: Ricardo Ribalda > --- > Documentation/admin-guide/kernel-parameters.txt | 14 > include/linux/kexec.h | 2 +- > kernel/kexec.c | 2 +- > kernel/kexec_core.c | 91 > - > kernel/kexec_file.c | 2 +- > 5 files changed, 106 insertions(+), 5 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt > b/Documentation/admin-guide/kernel-parameters.txt > index 42af9ca0127e..2b37d6a20747 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -2374,6 +2374,20 @@ > for Movable pages. "nn[KMGTPE]", "nn%", and "mirror" > are exclusive, so you cannot specify multiple forms. > > + kexec_core.load_limit_reboot= > + kexec_core.load_limit_panic= > + [KNL] > + This parameter specifies a limit to the number of times > + a kexec kernel can be loaded. > + Format: > + -1 = Unlimited. > + int = Number of times kexec can be called. > + > + During runtime, this parameter can be modified with a > + value smaller than the current one (but not -1). > + > + Default: -1 > + > kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. > Format: [,poll interval] > The controller # is the number of the ehci usb debug > diff --git a/include/linux/kexec.h b/include/linux/kexec.h > index e9e1ab5e8006..3d7d10f7187a 100644 > --- a/include/linux/kexec.h > +++ b/include/linux/kexec.h > @@ -407,7 +407,7 @@ extern int kimage_crash_copy_vmcoreinfo(struct kimage > *image); > extern struct kimage *kexec_image; > extern struct kimage *kexec_crash_image; > > -bool kexec_load_permited(void); > +bool kexec_load_permited(bool crash_image); > > #ifndef kexec_flush_icache_page > #define kexec_flush_icache_page(page) > diff --git a/kernel/kexec.c b/kernel/kexec.c > index d83fc9093aff..2b0856e83fe1 100644 > --- a/kernel/kexec.c > +++ b/kernel/kexec.c > @@ -193,7 +193,7 @@ static inline int kexec_load_check(unsigned long > nr_segments, > int result; > > /* We only trust the superuser with rebooting the system. */ > - if (!kexec_load_permited()) > + if (!kexec_load_permited(flags & KEXEC_ON_CRASH)) nit: permitted. > return -EPERM; > > /* Permit LSMs and IMA to fail the kexec */ > diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c > index 18bd90ca9c99..7f9d5288b24b 100644 > --- a/kernel/kexec_core.c > +++ b/kernel/kexec_core.c > @@ -952,13 +952,100 @@ static int __init kexec_core_sysctl_init(void) > late_initcall(kexec_core_sysctl_init); > #endif > > -bool kexec_load_permited(void) > +struct kexec_load_limit { > + /* Mutex protects the limit count. */ > + struct mutex mutex; > + int limit; Can you not just use atomic ops for limit, and get rid of the mutex? That will simplify the code as well. > +}; > + > +struct kexec_load_limit load_limit_reboot = { > + .mutex = __MUTEX_INITIALIZER(load_limit_reboot.mutex), > + .limit = -1, > +}; > + > +struct kexec_load_limit load_limit_panic = { > + .mutex = __MUTEX_INITIALIZER(load_limit_panic.mutex), > + .limit = -1, > +}; > + > +static int param_get_limit(char *buffer, const struct kernel_param *kp) > { > + int ret; > + struct kexec_load_limit *limit = kp->arg; > + > + mutex_lock(>mutex); > + ret = scnprintf(buffer, PAGE_SIZE, "%i\n", limit->limit); > + mutex_unlock(>mutex); > + > + return ret; > +} > + > +static int param_set_limit(const char *buffer, const struct kernel_param *kp) > +{ > + int ret; > + struct kexec_load_limit *limit = kp->arg; > + int new_val; > + > + ret = kstrtoint(buffer, 0, _val); > + if (ret) > + return ret; > + > + new_val = max(-1, new_val); > + > + mutex_lock(>mutex); > + > + if (new_val == -1 && limit->limit != -1) { > + ret = -EINVAL; > + goto done; > + } > + > + if (limit->limit != -1 && new_val > limit->limit) { > + ret = -EINVAL; > + goto done; > + } > + > + limit->limit = new_val; > + > +done: > + mutex_unlock(>mutex); > + > + return ret; > +} > + > +static const struct kernel_param_ops load_limit_ops = { > + .get = param_get_limit, > + .set = param_set_limit, >
[PATCH v2 3/3] kexec: Introduce paramters load_limit_reboot and load_limit_panic
Add two parameter to specify how many times a kexec kernel can be loaded. The sysadmin can set different limits for kexec panic and kexec reboot kernels. The value can be modified at runtime via sysfs, but only with a value smaller than the current one (except -1). Signed-off-by: Ricardo Ribalda --- Documentation/admin-guide/kernel-parameters.txt | 14 include/linux/kexec.h | 2 +- kernel/kexec.c | 2 +- kernel/kexec_core.c | 91 - kernel/kexec_file.c | 2 +- 5 files changed, 106 insertions(+), 5 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 42af9ca0127e..2b37d6a20747 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2374,6 +2374,20 @@ for Movable pages. "nn[KMGTPE]", "nn%", and "mirror" are exclusive, so you cannot specify multiple forms. + kexec_core.load_limit_reboot= + kexec_core.load_limit_panic= + [KNL] + This parameter specifies a limit to the number of times + a kexec kernel can be loaded. + Format: + -1 = Unlimited. + int = Number of times kexec can be called. + + During runtime, this parameter can be modified with a + value smaller than the current one (but not -1). + + Default: -1 + kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. Format: [,poll interval] The controller # is the number of the ehci usb debug diff --git a/include/linux/kexec.h b/include/linux/kexec.h index e9e1ab5e8006..3d7d10f7187a 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -407,7 +407,7 @@ extern int kimage_crash_copy_vmcoreinfo(struct kimage *image); extern struct kimage *kexec_image; extern struct kimage *kexec_crash_image; -bool kexec_load_permited(void); +bool kexec_load_permited(bool crash_image); #ifndef kexec_flush_icache_page #define kexec_flush_icache_page(page) diff --git a/kernel/kexec.c b/kernel/kexec.c index d83fc9093aff..2b0856e83fe1 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -193,7 +193,7 @@ static inline int kexec_load_check(unsigned long nr_segments, int result; /* We only trust the superuser with rebooting the system. */ - if (!kexec_load_permited()) + if (!kexec_load_permited(flags & KEXEC_ON_CRASH)) return -EPERM; /* Permit LSMs and IMA to fail the kexec */ diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index 18bd90ca9c99..7f9d5288b24b 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -952,13 +952,100 @@ static int __init kexec_core_sysctl_init(void) late_initcall(kexec_core_sysctl_init); #endif -bool kexec_load_permited(void) +struct kexec_load_limit { + /* Mutex protects the limit count. */ + struct mutex mutex; + int limit; +}; + +struct kexec_load_limit load_limit_reboot = { + .mutex = __MUTEX_INITIALIZER(load_limit_reboot.mutex), + .limit = -1, +}; + +struct kexec_load_limit load_limit_panic = { + .mutex = __MUTEX_INITIALIZER(load_limit_panic.mutex), + .limit = -1, +}; + +static int param_get_limit(char *buffer, const struct kernel_param *kp) { + int ret; + struct kexec_load_limit *limit = kp->arg; + + mutex_lock(>mutex); + ret = scnprintf(buffer, PAGE_SIZE, "%i\n", limit->limit); + mutex_unlock(>mutex); + + return ret; +} + +static int param_set_limit(const char *buffer, const struct kernel_param *kp) +{ + int ret; + struct kexec_load_limit *limit = kp->arg; + int new_val; + + ret = kstrtoint(buffer, 0, _val); + if (ret) + return ret; + + new_val = max(-1, new_val); + + mutex_lock(>mutex); + + if (new_val == -1 && limit->limit != -1) { + ret = -EINVAL; + goto done; + } + + if (limit->limit != -1 && new_val > limit->limit) { + ret = -EINVAL; + goto done; + } + + limit->limit = new_val; + +done: + mutex_unlock(>mutex); + + return ret; +} + +static const struct kernel_param_ops load_limit_ops = { + .get = param_get_limit, + .set = param_set_limit, +}; + +module_param_cb(load_limit_reboot, _limit_ops, _limit_reboot, 0644); +MODULE_PARM_DESC(load_limit_reboot, "Maximum attempts to load a kexec reboot kernel"); + +module_param_cb(load_limit_panic, _limit_ops, _limit_panic, 0644); +MODULE_PARM_DESC(load_limit_reboot, "Maximum attempts to load a kexec panic kernel"); + +bool kexec_load_permited(bool crash_image) +{ +