| Message ID | 20250110153918.241810-1-mic@digikod.net (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v1,1/2] landlock: Handle weird files | expand |
On Fri, Jan 10, 2025 at 04:39:13PM +0100, Mickaël Salaün wrote: > A corrupted filesystem (e.g. bcachefs) might return weird files. > Instead of throwing a warning and allowing access to such file, treat > them as regular files. > > Cc: Dave Chinner <david@fromorbit.com> > Cc: Günther Noack <gnoack@google.com> > Cc: Kent Overstreet <kent.overstreet@linux.dev> > Cc: Paul Moore <paul@paul-moore.com> > Reported-by: syzbot+34b68f850391452207df@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/r/000000000000a65b35061cffca61@google.com > Reported-by: syzbot+360866a59e3c80510a62@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/r/67379b3f.050a0220.85a0.0001.GAE@google.com > Reported-by: Ubisectech Sirius <bugreport@ubisectech.com> > Closes: https://lore.kernel.org/r/c426821d-8380-46c4-a494-7008bbd7dd13.bugreport@ubisectech.com > Fixes: cb2c7d1a1776 ("landlock: Support filesystem access-control") > Signed-off-by: Mickaël Salaün <mic@digikod.net> > --- > security/landlock/fs.c | 11 +++++------ > 1 file changed, 5 insertions(+), 6 deletions(-) > > diff --git a/security/landlock/fs.c b/security/landlock/fs.c > index e31b97a9f175..7adb25150488 100644 > --- a/security/landlock/fs.c > +++ b/security/landlock/fs.c > @@ -937,10 +937,6 @@ static access_mask_t get_mode_access(const umode_t mode) > switch (mode & S_IFMT) { > case S_IFLNK: > return LANDLOCK_ACCESS_FS_MAKE_SYM; > - case 0: > - /* A zero mode translates to S_IFREG. */ > - case S_IFREG: > - return LANDLOCK_ACCESS_FS_MAKE_REG; > case S_IFDIR: > return LANDLOCK_ACCESS_FS_MAKE_DIR; > case S_IFCHR: > @@ -951,9 +947,12 @@ static access_mask_t get_mode_access(const umode_t mode) > return LANDLOCK_ACCESS_FS_MAKE_FIFO; > case S_IFSOCK: > return LANDLOCK_ACCESS_FS_MAKE_SOCK; > + case S_IFREG: > + case 0: > + /* A zero mode translates to S_IFREG. */ > default: > - WARN_ON_ONCE(1); > - return 0; > + /* Treats weird files as regular files. */ > + return LANDLOCK_ACCESS_FS_MAKE_REG; > } > } > > -- > 2.47.1 > Reviewed-by: Günther Noack <gnoack3000@gmail.com> Makes sense to me, since this is enforcing a stronger check than before and can only happen in the case of corruption. I do not have a good intuition about what happens afterwards when the file system is in such a state. I imagine that this will usually give an error shortly afterwards, as the opening of the file continues? Is that right? –Günther
On Fri, Jan 10, 2025 at 05:37:26PM +0100, Günther Noack wrote: > On Fri, Jan 10, 2025 at 04:39:13PM +0100, Mickaël Salaün wrote: > > A corrupted filesystem (e.g. bcachefs) might return weird files. > > Instead of throwing a warning and allowing access to such file, treat > > them as regular files. > > > > Cc: Dave Chinner <david@fromorbit.com> > > Cc: Günther Noack <gnoack@google.com> > > Cc: Kent Overstreet <kent.overstreet@linux.dev> > > Cc: Paul Moore <paul@paul-moore.com> > > Reported-by: syzbot+34b68f850391452207df@syzkaller.appspotmail.com > > Closes: https://lore.kernel.org/r/000000000000a65b35061cffca61@google.com > > Reported-by: syzbot+360866a59e3c80510a62@syzkaller.appspotmail.com > > Closes: https://lore.kernel.org/r/67379b3f.050a0220.85a0.0001.GAE@google.com > > Reported-by: Ubisectech Sirius <bugreport@ubisectech.com> > > Closes: https://lore.kernel.org/r/c426821d-8380-46c4-a494-7008bbd7dd13.bugreport@ubisectech.com > > Fixes: cb2c7d1a1776 ("landlock: Support filesystem access-control") > > Signed-off-by: Mickaël Salaün <mic@digikod.net> > > --- > > security/landlock/fs.c | 11 +++++------ > > 1 file changed, 5 insertions(+), 6 deletions(-) > > > > diff --git a/security/landlock/fs.c b/security/landlock/fs.c > > index e31b97a9f175..7adb25150488 100644 > > --- a/security/landlock/fs.c > > +++ b/security/landlock/fs.c > > @@ -937,10 +937,6 @@ static access_mask_t get_mode_access(const umode_t mode) > > switch (mode & S_IFMT) { > > case S_IFLNK: > > return LANDLOCK_ACCESS_FS_MAKE_SYM; > > - case 0: > > - /* A zero mode translates to S_IFREG. */ > > - case S_IFREG: > > - return LANDLOCK_ACCESS_FS_MAKE_REG; > > case S_IFDIR: > > return LANDLOCK_ACCESS_FS_MAKE_DIR; > > case S_IFCHR: > > @@ -951,9 +947,12 @@ static access_mask_t get_mode_access(const umode_t mode) > > return LANDLOCK_ACCESS_FS_MAKE_FIFO; > > case S_IFSOCK: > > return LANDLOCK_ACCESS_FS_MAKE_SOCK; > > + case S_IFREG: > > + case 0: > > + /* A zero mode translates to S_IFREG. */ > > default: > > - WARN_ON_ONCE(1); > > - return 0; > > + /* Treats weird files as regular files. */ > > + return LANDLOCK_ACCESS_FS_MAKE_REG; > > } > > } > > > > -- > > 2.47.1 > > > > Reviewed-by: Günther Noack <gnoack3000@gmail.com> > > Makes sense to me, since this is enforcing a stronger check than before > and can only happen in the case of corruption. > > I do not have a good intuition about what happens afterwards when the > file system is in such a state. I imagine that this will usually give > an error shortly afterwards, as the opening of the file continues? Is > that right? I guess it depends on the filesystem implementation. For instance, XFS returns an error if a weird file is detected [1], whereas bcachefs ignores it (which is considered a bug, but not fixed yet) [2]. [1] https://lore.kernel.org/all/Zpc46HEacI%2Fwd7Rg@dread.disaster.area/ [2] https://lore.kernel.org/all/4hohnthh54adx35lnxzedop3oxpntpmtygxso4iraiexfdlt4d@6m7ssepvjyar/ > > –Günther >
On Sat, Jan 11, 2025 at 04:38:56PM +0100, Mickaël Salaün wrote: > I guess it depends on the filesystem implementation. For instance, XFS > returns an error if a weird file is detected [1], whereas bcachefs > ignores it (which is considered a bug, but not fixed yet) [2]. If a filesyste, returns an invalid mode that's a file system bug and needs to be fixed there. Warning in a consumer is perfectly fine. But the right action in that case is indeed not to grant the access.
On Tue, Jan 14, 2025 at 11:15:42PM -0800, Christoph Hellwig wrote: > On Sat, Jan 11, 2025 at 04:38:56PM +0100, Mickaël Salaün wrote: > > I guess it depends on the filesystem implementation. For instance, XFS > > returns an error if a weird file is detected [1], whereas bcachefs > > ignores it (which is considered a bug, but not fixed yet) [2]. > > If a filesyste, returns an invalid mode that's a file system bug and > needs to be fixed there. Warning in a consumer is perfectly fine. > But the right action in that case is indeed not to grant the access. Fyi, anonymous inodes traditionally set the mode to 0 which is really annoying: lrwx------ 1 root root 64 15. Jan 11:52 94 -> anon_inode:bpf-prog > sudo stat -L /proc/1/fd/94 File: /proc/1/fd/94 Size: 0 Blocks: 0 IO Block: 4096 weird file Device: 0,15 Inode: 4120 Links: 1 Access: (0600/?rw-------) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2024-11-05 17:15:54.404000000 +0100 Modify: 2024-11-05 17:15:54.404000000 +0100 Change: 2024-11-05 17:15:54.404000000 +0100 Birth: -
diff --git a/security/landlock/fs.c b/security/landlock/fs.c index e31b97a9f175..7adb25150488 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -937,10 +937,6 @@ static access_mask_t get_mode_access(const umode_t mode) switch (mode & S_IFMT) { case S_IFLNK: return LANDLOCK_ACCESS_FS_MAKE_SYM; - case 0: - /* A zero mode translates to S_IFREG. */ - case S_IFREG: - return LANDLOCK_ACCESS_FS_MAKE_REG; case S_IFDIR: return LANDLOCK_ACCESS_FS_MAKE_DIR; case S_IFCHR: @@ -951,9 +947,12 @@ static access_mask_t get_mode_access(const umode_t mode) return LANDLOCK_ACCESS_FS_MAKE_FIFO; case S_IFSOCK: return LANDLOCK_ACCESS_FS_MAKE_SOCK; + case S_IFREG: + case 0: + /* A zero mode translates to S_IFREG. */ default: - WARN_ON_ONCE(1); - return 0; + /* Treats weird files as regular files. */ + return LANDLOCK_ACCESS_FS_MAKE_REG; } }
A corrupted filesystem (e.g. bcachefs) might return weird files. Instead of throwing a warning and allowing access to such file, treat them as regular files. Cc: Dave Chinner <david@fromorbit.com> Cc: Günther Noack <gnoack@google.com> Cc: Kent Overstreet <kent.overstreet@linux.dev> Cc: Paul Moore <paul@paul-moore.com> Reported-by: syzbot+34b68f850391452207df@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/000000000000a65b35061cffca61@google.com Reported-by: syzbot+360866a59e3c80510a62@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/67379b3f.050a0220.85a0.0001.GAE@google.com Reported-by: Ubisectech Sirius <bugreport@ubisectech.com> Closes: https://lore.kernel.org/r/c426821d-8380-46c4-a494-7008bbd7dd13.bugreport@ubisectech.com Fixes: cb2c7d1a1776 ("landlock: Support filesystem access-control") Signed-off-by: Mickaël Salaün <mic@digikod.net> --- security/landlock/fs.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-)