sysctl: control functionality of /proc/pid/mem
Subsystems (3)
PATCH v2 1/1 sysctl: control functionality of /proc/pid/mem
Add the "proc_pid_mem" sysctl to control whether or not /proc/pid/mem is allowed to work: 0: disabled, 1: read only, 2: read/write.
Signed-off-by Kees Cook <[email protected]>
--- Documentation/sysctl/kernel.txt | 14 ++++++++++++++ fs/proc/base.c | 14 +++++++++++++- kernel/sysctl.c | 14 ++++++++++++++ 3 files changed, 41 insertions(+), 1 deletions(-)
Documentation/sysctl/kernel.txt +14 -0
@@ -56,6 +56,7 @@ show up in /proc/sys/kernel: - printk_delay - printk_ratelimit - printk_ratelimit_burst +- proc_pid_mem - randomize_va_space - real-root-dev ==> Documentation/initrd.txt - reboot-cmd [ SPARC only ]
@@ -477,6 +478,19 @@ send before ratelimiting kicks in. ============================================================== +proc_pid_mem: + +This option can be used to select the level of access given to potential +ptracers when using the per-process "mem" file in /proc/pid/mem. + +0 - Disable entirely. + +1 - Allow potential ptracers read access to process memory, but not writes. + +2 - Allow potential ptracers read and write access to process memory. + +============================================================== + randomize_va_space: This option can be used to select the type of process address
fs/proc/base.c +13 -1
@@ -109,6 +109,8 @@ struct pid_entry {union proc_op op; }; +int sysctl_proc_pid_mem =2 ; +#define NOD (NAME ,MODE ,IOP ,FOP ,OP ) { \ .name = (NAME), \ .len = sizeof(NAME) - 1, \
@@ -699,9 +701,13 @@ static const struct file_operations proc_single_file_operations = {static int mem_open (struct inode * inode,struct file * file) { -struct task_struct *task =get_proc_task (file->f_path.dentry->d_inode); +struct task_struct *task;struct mm_struct *mm; +if (sysctl_proc_pid_mem <1 ) +return -EACCES ; + + task =get_proc_task (file->f_path.dentry->d_inode);if (!task)return -ESRCH ;
@@ -726,6 +732,9 @@ static ssize_t mem_read(struct file * file, char __user * buf,unsigned long src = *ppos;struct mm_struct *mm = file->private_data; +if (sysctl_proc_pid_mem <1 ) +return -EACCES ; +if (!mm)return 0 ;
@@ -770,6 +779,9 @@ static ssize_t mem_write(struct file * file, const char __user *buf,unsigned long dst = *ppos;struct mm_struct *mm = file->private_data; +if (sysctl_proc_pid_mem <2 ) +return -EACCES ; +if (!mm)return 0 ;
kernel/sysctl.c +14 -0
@@ -109,6 +109,9 @@ extern int sysctl_nr_trim_pages;#ifdef CONFIG_BLOCK extern int blk_iopoll_enabled;#endif +#ifdef CONFIG_PROC_FS +extern int sysctl_proc_pid_mem; +#endif /* Constants used for minimum and maximum */ #ifdef CONFIG_LOCKUP_DETECTOR
@@ -1004,6 +1007,17 @@ static struct ctl_table kern_table[] = { .proc_handler = proc_dointvec, },#endif +#ifdef CONFIG_PROC_FS + { + .procname = "proc_pid_mem", + .data = &sysctl_proc_pid_mem, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = &zero, + .extra2 = &two, + }, +#endif { } };
Signature · 1 line
1.7.0.4
Quoted 2 lines · Kees Cook
Add the "
proc_pid_mem" sysctl to control whether or not/proc/pid/memis allowed to work: 0: disabled, 1: read only, 2: read/write.
Maybe mention that the default is 2 (or did you mean to change that sooner or later?).
Quoted 6 lines
Signed-off-by Kees Cook <[email protected]>--- Documentation/sysctl/kernel.txt | 14 ++++++++++++++ fs/proc/base.c | 14 +++++++++++++- kernel/sysctl.c | 14 ++++++++++++++ 3 files changed, 41 insertions(+), 1 deletions(-)
Signature · 2 lines
~Randy *** Remember to use Documentation/SubmitChecklist when testing your code ***
Quoted 105 lines · Kees Cook
Add the "
proc_pid_mem" sysctl to control whether or not/proc/pid/memis allowed to work: 0: disabled, 1: read only, 2: read/write.Signed-off-by Kees Cook <[email protected]>--- Documentation/sysctl/kernel.txt | 14 ++++++++++++++ fs/proc/base.c | 14 +++++++++++++- kernel/sysctl.c | 14 ++++++++++++++ 3 files changed, 41 insertions(+), 1 deletions(-)Documentation/sysctl/kernel.txt +14
-0@@ -56,6 +56,7 @@ show up in /proc/sys/kernel: - printk_delay - printk_ratelimit - printk_ratelimit_burst +- proc_pid_mem - randomize_va_space - real-root-dev ==> Documentation/initrd.txt - reboot-cmd [ SPARC only ]@@ -477,6 +478,19 @@ send before ratelimiting kicks in. ============================================================== +proc_pid_mem: + +This option can be used to select the level of access given to potential +ptracers when using the per-process "mem" file in /proc/pid/mem. + +0 - Disable entirely. + +1 - Allow potential ptracers read access to process memory, but not writes. + +2 - Allow potential ptracers read and write access to process memory. + +============================================================== + randomize_va_space: This option can be used to select the type of process addressfs/proc/base.c +13
-1@@ -109,6 +109,8 @@ struct pid_entry {union proc_op op; }; +int sysctl_proc_pid_mem =2 ; +#define NOD (NAME ,MODE ,IOP ,FOP ,OP ) { \ .name = (NAME), \ .len = sizeof(NAME) - 1, \@@ -699,9 +701,13 @@ static const struct file_operations proc_single_file_operations = {static int mem_open (struct inode * inode,struct file * file) { -struct task_struct *task =get_proc_task (file->f_path.dentry->d_inode); +struct task_struct *task;struct mm_struct *mm; +if (sysctl_proc_pid_mem <1 ) +return -EACCES ; + + task =get_proc_task (file->f_path.dentry->d_inode);if (!task)return -ESRCH ;@@ -726,6 +732,9 @@ static ssize_t mem_read(struct file * file, char __user * buf,unsigned long src = *ppos;struct mm_struct *mm = file->private_data; +if (sysctl_proc_pid_mem <1 ) +return -EACCES ; +if (!mm)return 0 ;@@ -770,6 +779,9 @@ static ssize_t mem_write(struct file * file, const char __user *buf,unsigned long dst = *ppos;struct mm_struct *mm = file->private_data; +if (sysctl_proc_pid_mem <2 ) +return -EACCES ; +if (!mm)return 0 ;kernel/sysctl.c +3
-0@@ -109,6 +109,9 @@ extern int sysctl_nr_trim_pages;#ifdef CONFIG_BLOCK extern int blk_iopoll_enabled;#endif +#ifdef CONFIG_PROC_FS +extern int sysctl_proc_pid_mem; +#endif /* Constants used for minimum and maximum */ #ifdef CONFIG_LOCKUP_DETECTOR
kernel/sysctl.c static struct ctl_table kern_table[] = { · line 1010
Quoted 4 lines
kernel/sysctl.c +1
-0@@ -1004,6 +1007,17 @@ static struct ctl_table kern_table[] = { .proc_handler = proc_dointvec, },#endif +#ifdef CONFIG_PROC_FS
^^^^^^^^^^^^^^^^^^^^^^
That ifdef is entertaining. CONFIG_SYSCTL depends on CONFIG_PROC_FS so which interesting case did you imagine this ifdef would be false? Did you test to ensure the code is not compiled in that interesting case?
Quoted 12 lines
kernel/sysctl.c +10
-0+ { + .procname = "proc_pid_mem", + .data = &sysctl_proc_pid_mem, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = &zero, + .extra2 = &two, + }, +#endif { } };
Quoted 6 lines · Eric W. Biederman
Quoted 1 line
+#ifdef
CONFIG_PROC_FS^^^^^^^^^^^^^^^^^^^^^^
That ifdef is entertaining. CONFIG_SYSCTL depends on
CONFIG_PROC_FSso which interesting case did you imagine this ifdef would be false? Did you test to ensure the code is not compiled in that interesting case?
I noticed that when I added it, and decided to err on the side of more configs if some day /proc/sys got moved out of /proc. Anyway, I can easily remove it. v3 coming up...
-Kees
Signature · 2 lines
Kees Cook ChromeOS Security