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authorJoe Lawrence <joe.lawrence@redhat.com>2017-11-17 15:29:24 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-11-17 16:10:03 -0800
commit7a8d181949fb2c16be00f8cdb354794a30e46b39 (patch)
tree4f18ea1b17605e97a2c5a0089ff819eb60435bc9
parentd3f14c485867cfb2e0c48aa88c41d0ef4bf5209c (diff)
pipe: add proc_dopipe_max_size() to safely assign pipe_max_size
pipe_max_size is assigned directly via procfs sysctl: static struct ctl_table fs_table[] = { ... { .procname = "pipe-max-size", .data = &pipe_max_size, .maxlen = sizeof(int), .mode = 0644, .proc_handler = &pipe_proc_fn, .extra1 = &pipe_min_size, }, ... int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf, size_t *lenp, loff_t *ppos) { ... ret = proc_dointvec_minmax(table, write, buf, lenp, ppos) ... and then later rounded in-place a few statements later: ... pipe_max_size = round_pipe_size(pipe_max_size); ... This leaves a window of time between initial assignment and rounding that may be visible to other threads. (For example, one thread sets a non-rounded value to pipe_max_size while another reads its value.) Similar reads of pipe_max_size are potentially racy: pipe.c :: alloc_pipe_info() pipe.c :: pipe_set_size() Add a new proc_dopipe_max_size() that consolidates reading the new value from the user buffer, verifying bounds, and calling round_pipe_size() with a single assignment to pipe_max_size. Link: http://lkml.kernel.org/r/1507658689-11669-4-git-send-email-joe.lawrence@redhat.com Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com> Reported-by: Mikulas Patocka <mpatocka@redhat.com> Reviewed-by: Mikulas Patocka <mpatocka@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Jens Axboe <axboe@kernel.dk> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/pipe.c18
-rw-r--r--include/linux/pipe_fs_i.h1
-rw-r--r--include/linux/sysctl.h3
-rw-r--r--kernel/sysctl.c49
4 files changed, 56 insertions, 15 deletions
diff --git a/fs/pipe.c b/fs/pipe.c
index f0f4ab36c444..6d98566201ef 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -1020,7 +1020,7 @@ const struct file_operations pipefifo_fops = {
* Currently we rely on the pipe array holding a power-of-2 number
* of pages. Returns 0 on error.
*/
-static inline unsigned int round_pipe_size(unsigned int size)
+unsigned int round_pipe_size(unsigned int size)
{
unsigned long nr_pages;
@@ -1125,25 +1125,13 @@ out_revert_acct:
}
/*
- * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
+ * This should work even if CONFIG_PROC_FS isn't set, as proc_dopipe_max_size
* will return an error.
*/
int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
size_t *lenp, loff_t *ppos)
{
- unsigned int rounded_pipe_max_size;
- int ret;
-
- ret = proc_douintvec_minmax(table, write, buf, lenp, ppos);
- if (ret < 0 || !write)
- return ret;
-
- rounded_pipe_max_size = round_pipe_size(pipe_max_size);
- if (rounded_pipe_max_size == 0)
- return -EINVAL;
-
- pipe_max_size = rounded_pipe_max_size;
- return ret;
+ return proc_dopipe_max_size(table, write, buf, lenp, ppos);
}
/*
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 6a80cfc63e0c..2dc5e9870fcd 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -191,5 +191,6 @@ long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
struct pipe_inode_info *get_pipe_info(struct file *file);
int create_pipe_files(struct file **, int);
+unsigned int round_pipe_size(unsigned int size);
#endif
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index b769ecfcc3bd..992bc9948232 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -51,6 +51,9 @@ extern int proc_dointvec_minmax(struct ctl_table *, int,
extern int proc_douintvec_minmax(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos);
+extern int proc_dopipe_max_size(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos);
extern int proc_dointvec_jiffies(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
extern int proc_dointvec_userhz_jiffies(struct ctl_table *, int,
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 2d42183b4c98..138b6484f277 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -66,6 +66,7 @@
#include <linux/kexec.h>
#include <linux/bpf.h>
#include <linux/mount.h>
+#include <linux/pipe_fs_i.h>
#include <linux/uaccess.h>
#include <asm/processor.h>
@@ -2620,6 +2621,47 @@ int proc_douintvec_minmax(struct ctl_table *table, int write,
do_proc_douintvec_minmax_conv, &param);
}
+struct do_proc_dopipe_max_size_conv_param {
+ unsigned int *min;
+};
+
+static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
+ unsigned int *valp,
+ int write, void *data)
+{
+ struct do_proc_dopipe_max_size_conv_param *param = data;
+
+ if (write) {
+ unsigned int val = round_pipe_size(*lvalp);
+
+ if (val == 0)
+ return -EINVAL;
+
+ if (param->min && *param->min > val)
+ return -ERANGE;
+
+ if (*lvalp > UINT_MAX)
+ return -EINVAL;
+
+ *valp = val;
+ } else {
+ unsigned int val = *valp;
+ *lvalp = (unsigned long) val;
+ }
+
+ return 0;
+}
+
+int proc_dopipe_max_size(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct do_proc_dopipe_max_size_conv_param param = {
+ .min = (unsigned int *) table->extra1,
+ };
+ return do_proc_douintvec(table, write, buffer, lenp, ppos,
+ do_proc_dopipe_max_size_conv, &param);
+}
+
static void validate_coredump_safety(void)
{
#ifdef CONFIG_COREDUMP
@@ -3125,6 +3167,12 @@ int proc_douintvec_minmax(struct ctl_table *table, int write,
return -ENOSYS;
}
+int proc_dopipe_max_size(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ return -ENOSYS;
+}
+
int proc_dointvec_jiffies(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
@@ -3168,6 +3216,7 @@ EXPORT_SYMBOL(proc_douintvec);
EXPORT_SYMBOL(proc_dointvec_jiffies);
EXPORT_SYMBOL(proc_dointvec_minmax);
EXPORT_SYMBOL_GPL(proc_douintvec_minmax);
+EXPORT_SYMBOL_GPL(proc_dopipe_max_size);
EXPORT_SYMBOL(proc_dointvec_userhz_jiffies);
EXPORT_SYMBOL(proc_dointvec_ms_jiffies);
EXPORT_SYMBOL(proc_dostring);