* [PATCH v2 0/2] proc: Relax check of mount visibility @ 2020-08-19 19:14 Alexey Gladkov 2020-08-19 19:14 ` [PATCH v2 1/2] " Alexey Gladkov 2020-08-19 19:14 ` [PATCH v2 2/2] Show /proc/self/net only for CAP_NET_ADMIN Alexey Gladkov 0 siblings, 2 replies; 7+ messages in thread From: Alexey Gladkov @ 2020-08-19 19:14 UTC (permalink / raw) To: LKML, Linux FS Devel, Eric W . Biederman Cc: Alexey Gladkov, Alexander Viro, Kees Cook If only the dynamic part of procfs is mounted (subset=pid), then there is no need to check if procfs is fully visible to the user in the new user namespace. Alexey Gladkov (2): proc: Relax check of mount visibility Show /proc/self/net only for CAP_NET_ADMIN fs/namespace.c | 27 ++++++++++++++++----------- fs/proc/proc_net.c | 8 ++++++++ fs/proc/root.c | 21 +++++++++++++++------ include/linux/fs.h | 1 + include/linux/proc_fs.h | 1 + 5 files changed, 41 insertions(+), 17 deletions(-) -- 2.25.4 ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v2 1/2] proc: Relax check of mount visibility 2020-08-19 19:14 [PATCH v2 0/2] proc: Relax check of mount visibility Alexey Gladkov @ 2020-08-19 19:14 ` Alexey Gladkov 2020-08-19 19:14 ` [PATCH v2 2/2] Show /proc/self/net only for CAP_NET_ADMIN Alexey Gladkov 1 sibling, 0 replies; 7+ messages in thread From: Alexey Gladkov @ 2020-08-19 19:14 UTC (permalink / raw) To: LKML, Linux FS Devel, Eric W . Biederman Cc: Alexey Gladkov, Alexander Viro, Kees Cook Allow to mount of procfs with subset=pid option even if the entire procfs is not fully accessible to the user. Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com> --- fs/namespace.c | 27 ++++++++++++++++----------- fs/proc/root.c | 16 +++++++++------- include/linux/fs.h | 1 + 3 files changed, 26 insertions(+), 18 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 4a0f600a3328..ab9d607921da 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3949,18 +3949,23 @@ static bool mnt_already_visible(struct mnt_namespace *ns, ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK))) continue; - /* This mount is not fully visible if there are any - * locked child mounts that cover anything except for - * empty directories. + /* If this filesystem is completely dynamic, then it + * makes no sense to check for any child mounts. */ - list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { - struct inode *inode = child->mnt_mountpoint->d_inode; - /* Only worry about locked mounts */ - if (!(child->mnt.mnt_flags & MNT_LOCKED)) - continue; - /* Is the directory permanetly empty? */ - if (!is_empty_dir_inode(inode)) - goto next; + if (!(sb->s_iflags & SB_I_DYNAMIC)) { + /* This mount is not fully visible if there are any + * locked child mounts that cover anything except for + * empty directories. + */ + list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { + struct inode *inode = child->mnt_mountpoint->d_inode; + /* Only worry about locked mounts */ + if (!(child->mnt.mnt_flags & MNT_LOCKED)) + continue; + /* Is the directory permanetly empty? */ + if (!is_empty_dir_inode(inode)) + goto next; + } } /* Preserve the locked attributes */ *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \ diff --git a/fs/proc/root.c b/fs/proc/root.c index 5e444d4f9717..c6bf74de1906 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -145,18 +145,21 @@ static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) return 0; } -static void proc_apply_options(struct proc_fs_info *fs_info, +static void proc_apply_options(struct super_block *s, struct fs_context *fc, struct user_namespace *user_ns) { struct proc_fs_context *ctx = fc->fs_private; + struct proc_fs_info *fs_info = proc_sb_info(s); if (ctx->mask & (1 << Opt_gid)) fs_info->pid_gid = make_kgid(user_ns, ctx->gid); if (ctx->mask & (1 << Opt_hidepid)) fs_info->hide_pid = ctx->hidepid; - if (ctx->mask & (1 << Opt_subset)) + if (ctx->mask & (1 << Opt_subset)) { fs_info->pidonly = ctx->pidonly; + s->s_iflags |= SB_I_DYNAMIC; + } } static int proc_fill_super(struct super_block *s, struct fs_context *fc) @@ -170,9 +173,6 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc) if (!fs_info) return -ENOMEM; - fs_info->pid_ns = get_pid_ns(ctx->pid_ns); - proc_apply_options(fs_info, fc, current_user_ns()); - /* User space would break if executables or devices appear on proc */ s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV; s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC; @@ -183,6 +183,9 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc) s->s_time_gran = 1; s->s_fs_info = fs_info; + fs_info->pid_ns = get_pid_ns(ctx->pid_ns); + proc_apply_options(s, fc, current_user_ns()); + /* * procfs isn't actually a stacking filesystem; however, there is * too much magic going on inside it to permit stacking things on @@ -216,11 +219,10 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc) static int proc_reconfigure(struct fs_context *fc) { struct super_block *sb = fc->root->d_sb; - struct proc_fs_info *fs_info = proc_sb_info(sb); sync_filesystem(sb); - proc_apply_options(fs_info, fc, current_user_ns()); + proc_apply_options(sb, fc, current_user_ns()); return 0; } diff --git a/include/linux/fs.h b/include/linux/fs.h index f5abba86107d..aff5ed9e8f82 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1413,6 +1413,7 @@ extern int send_sigurg(struct fown_struct *fown); #define SB_I_USERNS_VISIBLE 0x00000010 /* fstype already mounted */ #define SB_I_IMA_UNVERIFIABLE_SIGNATURE 0x00000020 #define SB_I_UNTRUSTED_MOUNTER 0x00000040 +#define SB_I_DYNAMIC 0x00000080 #define SB_I_SKIP_SYNC 0x00000100 /* Skip superblock at global sync */ -- 2.25.4 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH v2 2/2] Show /proc/self/net only for CAP_NET_ADMIN 2020-08-19 19:14 [PATCH v2 0/2] proc: Relax check of mount visibility Alexey Gladkov 2020-08-19 19:14 ` [PATCH v2 1/2] " Alexey Gladkov @ 2020-08-19 19:14 ` Alexey Gladkov 2020-08-19 21:27 ` kernel test robot ` (2 more replies) 1 sibling, 3 replies; 7+ messages in thread From: Alexey Gladkov @ 2020-08-19 19:14 UTC (permalink / raw) To: LKML, Linux FS Devel, Eric W . Biederman Cc: Alexey Gladkov, Alexander Viro, Kees Cook Cache the mounters credentials and make access to the net directories contingent of the permissions of the mounter of proc. Show /proc/self/net only if mounter has CAP_NET_ADMIN and if proc is mounted with subset=pid option. Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com> --- fs/proc/proc_net.c | 8 ++++++++ fs/proc/root.c | 7 +++++++ include/linux/proc_fs.h | 1 + 3 files changed, 16 insertions(+) diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c index dba63b2429f0..c43fc5c907db 100644 --- a/fs/proc/proc_net.c +++ b/fs/proc/proc_net.c @@ -26,6 +26,7 @@ #include <linux/uidgid.h> #include <net/net_namespace.h> #include <linux/seq_file.h> +#include <linux/security.h> #include "internal.h" @@ -275,6 +276,7 @@ static struct net *get_proc_task_net(struct inode *dir) struct task_struct *task; struct nsproxy *ns; struct net *net = NULL; + struct proc_fs_info *fs_info = proc_sb_info(dir->i_sb); rcu_read_lock(); task = pid_task(proc_pid(dir), PIDTYPE_PID); @@ -287,6 +289,12 @@ static struct net *get_proc_task_net(struct inode *dir) } rcu_read_unlock(); + if (net && (fs_info->pidonly == PROC_PIDONLY_ON) && + security_capable(fs_info->mounter_cred, net->user_ns, CAP_NET_ADMIN, CAP_OPT_NONE) < 0) { + put_net(net); + net = NULL; + } + return net; } diff --git a/fs/proc/root.c b/fs/proc/root.c index c6bf74de1906..eeeda375cf85 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -184,6 +184,8 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc) s->s_fs_info = fs_info; fs_info->pid_ns = get_pid_ns(ctx->pid_ns); + fs_info->mounter_cred = get_cred(fc->cred); + proc_apply_options(s, fc, current_user_ns()); /* @@ -219,9 +221,13 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc) static int proc_reconfigure(struct fs_context *fc) { struct super_block *sb = fc->root->d_sb; + struct proc_fs_info *fs_info = proc_sb_info(sb); sync_filesystem(sb); + put_cred(fs_info->mounter_cred); + fs_info->mounter_cred = get_cred(fc->cred); + proc_apply_options(sb, fc, current_user_ns()); return 0; } @@ -276,6 +282,7 @@ static void proc_kill_sb(struct super_block *sb) kill_anon_super(sb); put_pid_ns(fs_info->pid_ns); + put_cred(fs_info->mounter_cred); kfree(fs_info); } diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h index d1eed1b43651..671c6dafc4ee 100644 --- a/include/linux/proc_fs.h +++ b/include/linux/proc_fs.h @@ -63,6 +63,7 @@ struct proc_fs_info { kgid_t pid_gid; enum proc_hidepid hide_pid; enum proc_pidonly pidonly; + struct cred *mounter_cred; }; static inline struct proc_fs_info *proc_sb_info(struct super_block *sb) -- 2.25.4 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH v2 2/2] Show /proc/self/net only for CAP_NET_ADMIN 2020-08-19 19:14 ` [PATCH v2 2/2] Show /proc/self/net only for CAP_NET_ADMIN Alexey Gladkov @ 2020-08-19 21:27 ` kernel test robot 2020-08-19 21:59 ` kernel test robot 2020-08-19 23:27 ` kernel test robot 2 siblings, 0 replies; 7+ messages in thread From: kernel test robot @ 2020-08-19 21:27 UTC (permalink / raw) To: Alexey Gladkov, LKML, Linux FS Devel, Eric W . Biederman Cc: kbuild-all, Alexey Gladkov, Alexander Viro, Kees Cook [-- Attachment #1: Type: text/plain, Size: 3986 bytes --] Hi Alexey, Thank you for the patch! Perhaps something to improve: [auto build test WARNING on linux/master] [also build test WARNING on kees/for-next/pstore linus/master v5.9-rc1 next-20200819] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch] url: https://github.com/0day-ci/linux/commits/Alexey-Gladkov/proc-Relax-check-of-mount-visibility/20200820-031542 base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git bcf876870b95592b52519ed4aafcf9d95999bc9c config: xtensa-allyesconfig (attached as .config) compiler: xtensa-linux-gcc (GCC) 9.3.0 reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=xtensa If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp@intel.com> All warnings (new ones prefixed by >>): fs/proc/root.c: In function 'proc_fill_super': >> fs/proc/root.c:187:24: warning: assignment discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers] 187 | fs_info->mounter_cred = get_cred(fc->cred); | ^ fs/proc/root.c: In function 'proc_reconfigure': fs/proc/root.c:229:24: warning: assignment discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers] 229 | fs_info->mounter_cred = get_cred(fc->cred); | ^ # https://github.com/0day-ci/linux/commit/9c2a0eea7f38b1a4e201b8f2da0c5fd7b423daf9 git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Alexey-Gladkov/proc-Relax-check-of-mount-visibility/20200820-031542 git checkout 9c2a0eea7f38b1a4e201b8f2da0c5fd7b423daf9 vim +/const +187 fs/proc/root.c 164 165 static int proc_fill_super(struct super_block *s, struct fs_context *fc) 166 { 167 struct proc_fs_context *ctx = fc->fs_private; 168 struct inode *root_inode; 169 struct proc_fs_info *fs_info; 170 int ret; 171 172 fs_info = kzalloc(sizeof(*fs_info), GFP_KERNEL); 173 if (!fs_info) 174 return -ENOMEM; 175 176 /* User space would break if executables or devices appear on proc */ 177 s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV; 178 s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC; 179 s->s_blocksize = 1024; 180 s->s_blocksize_bits = 10; 181 s->s_magic = PROC_SUPER_MAGIC; 182 s->s_op = &proc_sops; 183 s->s_time_gran = 1; 184 s->s_fs_info = fs_info; 185 186 fs_info->pid_ns = get_pid_ns(ctx->pid_ns); > 187 fs_info->mounter_cred = get_cred(fc->cred); 188 189 proc_apply_options(s, fc, current_user_ns()); 190 191 /* 192 * procfs isn't actually a stacking filesystem; however, there is 193 * too much magic going on inside it to permit stacking things on 194 * top of it 195 */ 196 s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH; 197 198 /* procfs dentries and inodes don't require IO to create */ 199 s->s_shrink.seeks = 0; 200 201 pde_get(&proc_root); 202 root_inode = proc_get_inode(s, &proc_root); 203 if (!root_inode) { 204 pr_err("proc_fill_super: get root inode failed\n"); 205 return -ENOMEM; 206 } 207 208 s->s_root = d_make_root(root_inode); 209 if (!s->s_root) { 210 pr_err("proc_fill_super: allocate dentry failed\n"); 211 return -ENOMEM; 212 } 213 214 ret = proc_setup_self(s); 215 if (ret) { 216 return ret; 217 } 218 return proc_setup_thread_self(s); 219 } 220 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org [-- Attachment #2: .config.gz --] [-- Type: application/gzip, Size: 64408 bytes --] ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2 2/2] Show /proc/self/net only for CAP_NET_ADMIN 2020-08-19 19:14 ` [PATCH v2 2/2] Show /proc/self/net only for CAP_NET_ADMIN Alexey Gladkov 2020-08-19 21:27 ` kernel test robot @ 2020-08-19 21:59 ` kernel test robot 2020-08-19 23:27 ` kernel test robot 2 siblings, 0 replies; 7+ messages in thread From: kernel test robot @ 2020-08-19 21:59 UTC (permalink / raw) To: Alexey Gladkov, LKML, Linux FS Devel, Eric W . Biederman Cc: kbuild-all, Alexey Gladkov, Alexander Viro, Kees Cook [-- Attachment #1: Type: text/plain, Size: 4177 bytes --] Hi Alexey, Thank you for the patch! Perhaps something to improve: [auto build test WARNING on linux/master] [also build test WARNING on kees/for-next/pstore linus/master v5.9-rc1 next-20200819] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch] url: https://github.com/0day-ci/linux/commits/Alexey-Gladkov/proc-Relax-check-of-mount-visibility/20200820-031542 base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git bcf876870b95592b52519ed4aafcf9d95999bc9c config: m68k-randconfig-s032-20200819 (attached as .config) compiler: m68k-linux-gcc (GCC) 9.3.0 reproduce: wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # apt-get install sparse # sparse version: v0.6.2-183-gaa6ede3b-dirty # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=m68k If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp@intel.com> sparse warnings: (new ones prefixed by >>) >> fs/proc/root.c:187:31: sparse: sparse: incorrect type in assignment (different modifiers) @@ expected struct cred *mounter_cred @@ got struct cred const * @@ >> fs/proc/root.c:187:31: sparse: expected struct cred *mounter_cred >> fs/proc/root.c:187:31: sparse: got struct cred const * fs/proc/root.c:229:31: sparse: sparse: incorrect type in assignment (different modifiers) @@ expected struct cred *mounter_cred @@ got struct cred const * @@ fs/proc/root.c:229:31: sparse: expected struct cred *mounter_cred fs/proc/root.c:229:31: sparse: got struct cred const * # https://github.com/0day-ci/linux/commit/9c2a0eea7f38b1a4e201b8f2da0c5fd7b423daf9 git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Alexey-Gladkov/proc-Relax-check-of-mount-visibility/20200820-031542 git checkout 9c2a0eea7f38b1a4e201b8f2da0c5fd7b423daf9 vim +187 fs/proc/root.c 164 165 static int proc_fill_super(struct super_block *s, struct fs_context *fc) 166 { 167 struct proc_fs_context *ctx = fc->fs_private; 168 struct inode *root_inode; 169 struct proc_fs_info *fs_info; 170 int ret; 171 172 fs_info = kzalloc(sizeof(*fs_info), GFP_KERNEL); 173 if (!fs_info) 174 return -ENOMEM; 175 176 /* User space would break if executables or devices appear on proc */ 177 s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV; 178 s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC; 179 s->s_blocksize = 1024; 180 s->s_blocksize_bits = 10; 181 s->s_magic = PROC_SUPER_MAGIC; 182 s->s_op = &proc_sops; 183 s->s_time_gran = 1; 184 s->s_fs_info = fs_info; 185 186 fs_info->pid_ns = get_pid_ns(ctx->pid_ns); > 187 fs_info->mounter_cred = get_cred(fc->cred); 188 189 proc_apply_options(s, fc, current_user_ns()); 190 191 /* 192 * procfs isn't actually a stacking filesystem; however, there is 193 * too much magic going on inside it to permit stacking things on 194 * top of it 195 */ 196 s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH; 197 198 /* procfs dentries and inodes don't require IO to create */ 199 s->s_shrink.seeks = 0; 200 201 pde_get(&proc_root); 202 root_inode = proc_get_inode(s, &proc_root); 203 if (!root_inode) { 204 pr_err("proc_fill_super: get root inode failed\n"); 205 return -ENOMEM; 206 } 207 208 s->s_root = d_make_root(root_inode); 209 if (!s->s_root) { 210 pr_err("proc_fill_super: allocate dentry failed\n"); 211 return -ENOMEM; 212 } 213 214 ret = proc_setup_self(s); 215 if (ret) { 216 return ret; 217 } 218 return proc_setup_thread_self(s); 219 } 220 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org [-- Attachment #2: .config.gz --] [-- Type: application/gzip, Size: 23980 bytes --] ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2 2/2] Show /proc/self/net only for CAP_NET_ADMIN 2020-08-19 19:14 ` [PATCH v2 2/2] Show /proc/self/net only for CAP_NET_ADMIN Alexey Gladkov 2020-08-19 21:27 ` kernel test robot 2020-08-19 21:59 ` kernel test robot @ 2020-08-19 23:27 ` kernel test robot 2 siblings, 0 replies; 7+ messages in thread From: kernel test robot @ 2020-08-19 23:27 UTC (permalink / raw) To: Alexey Gladkov, LKML, Linux FS Devel, Eric W . Biederman Cc: kbuild-all, clang-built-linux, Alexey Gladkov, Alexander Viro, Kees Cook [-- Attachment #1: Type: text/plain, Size: 4201 bytes --] Hi Alexey, Thank you for the patch! Yet something to improve: [auto build test ERROR on linux/master] [also build test ERROR on kees/for-next/pstore linus/master v5.9-rc1 next-20200819] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch] url: https://github.com/0day-ci/linux/commits/Alexey-Gladkov/proc-Relax-check-of-mount-visibility/20200820-031542 base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git bcf876870b95592b52519ed4aafcf9d95999bc9c config: s390-randconfig-r034-20200818 (attached as .config) compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project b34b1e38381fa4d1b1d9751a6b5233b68e734cfe) reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # install s390 cross compiling tool for clang build # apt-get install binutils-s390x-linux-gnu # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=s390 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp@intel.com> All errors (new ones prefixed by >>): >> fs/proc/root.c:187:24: error: assigning to 'struct cred *' from 'const struct cred *' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers] fs_info->mounter_cred = get_cred(fc->cred); ^ ~~~~~~~~~~~~~~~~~~ fs/proc/root.c:229:24: error: assigning to 'struct cred *' from 'const struct cred *' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers] fs_info->mounter_cred = get_cred(fc->cred); ^ ~~~~~~~~~~~~~~~~~~ 2 errors generated. # https://github.com/0day-ci/linux/commit/9c2a0eea7f38b1a4e201b8f2da0c5fd7b423daf9 git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Alexey-Gladkov/proc-Relax-check-of-mount-visibility/20200820-031542 git checkout 9c2a0eea7f38b1a4e201b8f2da0c5fd7b423daf9 vim +187 fs/proc/root.c 164 165 static int proc_fill_super(struct super_block *s, struct fs_context *fc) 166 { 167 struct proc_fs_context *ctx = fc->fs_private; 168 struct inode *root_inode; 169 struct proc_fs_info *fs_info; 170 int ret; 171 172 fs_info = kzalloc(sizeof(*fs_info), GFP_KERNEL); 173 if (!fs_info) 174 return -ENOMEM; 175 176 /* User space would break if executables or devices appear on proc */ 177 s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV; 178 s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC; 179 s->s_blocksize = 1024; 180 s->s_blocksize_bits = 10; 181 s->s_magic = PROC_SUPER_MAGIC; 182 s->s_op = &proc_sops; 183 s->s_time_gran = 1; 184 s->s_fs_info = fs_info; 185 186 fs_info->pid_ns = get_pid_ns(ctx->pid_ns); > 187 fs_info->mounter_cred = get_cred(fc->cred); 188 189 proc_apply_options(s, fc, current_user_ns()); 190 191 /* 192 * procfs isn't actually a stacking filesystem; however, there is 193 * too much magic going on inside it to permit stacking things on 194 * top of it 195 */ 196 s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH; 197 198 /* procfs dentries and inodes don't require IO to create */ 199 s->s_shrink.seeks = 0; 200 201 pde_get(&proc_root); 202 root_inode = proc_get_inode(s, &proc_root); 203 if (!root_inode) { 204 pr_err("proc_fill_super: get root inode failed\n"); 205 return -ENOMEM; 206 } 207 208 s->s_root = d_make_root(root_inode); 209 if (!s->s_root) { 210 pr_err("proc_fill_super: allocate dentry failed\n"); 211 return -ENOMEM; 212 } 213 214 ret = proc_setup_self(s); 215 if (ret) { 216 return ret; 217 } 218 return proc_setup_thread_self(s); 219 } 220 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org [-- Attachment #2: .config.gz --] [-- Type: application/gzip, Size: 29945 bytes --] ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v1 2/2] Show /proc/self/net only for CAP_NET_ADMIN
@ 2020-07-27 16:29 Eric W. Biederman
2020-07-31 16:10 ` [PATCH v2 " Alexey Gladkov
0 siblings, 1 reply; 7+ messages in thread
From: Eric W. Biederman @ 2020-07-27 16:29 UTC (permalink / raw)
To: Alexey Gladkov
Cc: LKML, Linux FS Devel, Alexander Viro, Alexey Gladkov, Kees Cook
Alexey Gladkov <gladkov.alexey@gmail.com> writes:
> Show /proc/self/net only for CAP_NET_ADMIN if procfs is mounted with
> subset=pid option in user namespace. This is done to avoid possible
> information leakage.
>
> Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>
> ---
> fs/proc/proc_net.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c
> index dba63b2429f0..11fa2c4b3529 100644
> --- a/fs/proc/proc_net.c
> +++ b/fs/proc/proc_net.c
> @@ -275,6 +275,12 @@ static struct net *get_proc_task_net(struct inode *dir)
> struct task_struct *task;
> struct nsproxy *ns;
> struct net *net = NULL;
> + struct proc_fs_info *fs_info = proc_sb_info(dir->i_sb);
> +
> + if ((fs_info->pidonly == PROC_PIDONLY_ON) &&
> + (current_user_ns() != &init_user_ns) &&
> + !capable(CAP_NET_ADMIN))
> + return net;
>
> rcu_read_lock();
> task = pid_task(proc_pid(dir), PIDTYPE_PID);
Hmm.
I see 3 options going forward.
1) We just make PROC_PIDONLY_ON mean the net directory does not exist.
No permission checks just always fail.
2) Move the permission checks into opendir/readdir and whichever
is the appropriate method there and always allow the dentries
to be cached.
3) Simply cache the mounters credentials and make access to the
net directories contingent of the permisions of the mounter of
proc. Something like the code below.
static struct net *get_proc_task_net(struct inode *dir)
{
struct task_struct *task;
struct nsproxy *ns;
struct net *net = NULL;
rcu_read_lock();
task = pid_task(proc_pid(dir), PIDTYPE_PID);
if (task != NULL) {
task_lock(task);
ns = task->nsproxy;
if (ns != NULL)
net = get_net(ns->net_ns);
task_unlock(task);
}
rcu_read_unlock();
if ((fs_info->pidonly == PROC_PIDONLY_ON) &&
!security_capable(fs_info->mounter_cred,
net->user_ns, CAP_SYS_ADMIN,
CAP_OPT_NONE)) {
put_net(net);
net = NULL;
}
return net;
}
Eric
^ permalink raw reply [flat|nested] 7+ messages in thread* [PATCH v2 2/2] Show /proc/self/net only for CAP_NET_ADMIN 2020-07-27 16:29 [PATCH v1 " Eric W. Biederman @ 2020-07-31 16:10 ` Alexey Gladkov 0 siblings, 0 replies; 7+ messages in thread From: Alexey Gladkov @ 2020-07-31 16:10 UTC (permalink / raw) To: LKML Cc: Linux FS Devel, Alexander Viro, Alexey Gladkov, Eric W . Biederman, Kees Cook Cache the mounters credentials and make access to the net directories contingent of the permissions of the mounter of proc. Show /proc/self/net only if mounter has CAP_NET_ADMIN and if proc is mounted with subset=pid option. Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com> --- fs/proc/proc_net.c | 8 ++++++++ fs/proc/root.c | 7 +++++++ include/linux/proc_fs.h | 1 + 3 files changed, 16 insertions(+) diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c index dba63b2429f0..c43fc5c907db 100644 --- a/fs/proc/proc_net.c +++ b/fs/proc/proc_net.c @@ -26,6 +26,7 @@ #include <linux/uidgid.h> #include <net/net_namespace.h> #include <linux/seq_file.h> +#include <linux/security.h> #include "internal.h" @@ -275,6 +276,7 @@ static struct net *get_proc_task_net(struct inode *dir) struct task_struct *task; struct nsproxy *ns; struct net *net = NULL; + struct proc_fs_info *fs_info = proc_sb_info(dir->i_sb); rcu_read_lock(); task = pid_task(proc_pid(dir), PIDTYPE_PID); @@ -287,6 +289,12 @@ static struct net *get_proc_task_net(struct inode *dir) } rcu_read_unlock(); + if (net && (fs_info->pidonly == PROC_PIDONLY_ON) && + security_capable(fs_info->mounter_cred, net->user_ns, CAP_NET_ADMIN, CAP_OPT_NONE) < 0) { + put_net(net); + net = NULL; + } + return net; } diff --git a/fs/proc/root.c b/fs/proc/root.c index c6bf74de1906..eeeda375cf85 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -184,6 +184,8 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc) s->s_fs_info = fs_info; fs_info->pid_ns = get_pid_ns(ctx->pid_ns); + fs_info->mounter_cred = get_cred(fc->cred); + proc_apply_options(s, fc, current_user_ns()); /* @@ -219,9 +221,13 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc) static int proc_reconfigure(struct fs_context *fc) { struct super_block *sb = fc->root->d_sb; + struct proc_fs_info *fs_info = proc_sb_info(sb); sync_filesystem(sb); + put_cred(fs_info->mounter_cred); + fs_info->mounter_cred = get_cred(fc->cred); + proc_apply_options(sb, fc, current_user_ns()); return 0; } @@ -276,6 +282,7 @@ static void proc_kill_sb(struct super_block *sb) kill_anon_super(sb); put_pid_ns(fs_info->pid_ns); + put_cred(fs_info->mounter_cred); kfree(fs_info); } diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h index d1eed1b43651..671c6dafc4ee 100644 --- a/include/linux/proc_fs.h +++ b/include/linux/proc_fs.h @@ -63,6 +63,7 @@ struct proc_fs_info { kgid_t pid_gid; enum proc_hidepid hide_pid; enum proc_pidonly pidonly; + struct cred *mounter_cred; }; static inline struct proc_fs_info *proc_sb_info(struct super_block *sb) -- 2.25.4 ^ permalink raw reply related [flat|nested] 7+ messages in thread
end of thread, other threads:[~2020-08-19 23:28 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-08-19 19:14 [PATCH v2 0/2] proc: Relax check of mount visibility Alexey Gladkov 2020-08-19 19:14 ` [PATCH v2 1/2] " Alexey Gladkov 2020-08-19 19:14 ` [PATCH v2 2/2] Show /proc/self/net only for CAP_NET_ADMIN Alexey Gladkov 2020-08-19 21:27 ` kernel test robot 2020-08-19 21:59 ` kernel test robot 2020-08-19 23:27 ` kernel test robot -- strict thread matches above, loose matches on Subject: below -- 2020-07-27 16:29 [PATCH v1 " Eric W. Biederman 2020-07-31 16:10 ` [PATCH v2 " Alexey Gladkov
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