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| author | Pavel Emelyanov <xemul@openvz.org> | 2008-04-29 00:59:24 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-04-29 08:06:04 -0700 |
| commit | 3a2e7f47d71e1df86acc1dda6826890b6546a4e1 (patch) | |
| tree | 3c5856f67af25a80a4d934e754f437936c7b1bbf | |
| parent | cbd9b67bd3883dff0ef4b8ec9229d315a9ba38f0 (diff) | |
| download | linux-stable-3a2e7f47d71e1df86acc1dda6826890b6546a4e1.tar.gz linux-stable-3a2e7f47d71e1df86acc1dda6826890b6546a4e1.tar.bz2 linux-stable-3a2e7f47d71e1df86acc1dda6826890b6546a4e1.zip | |
binfmt_misc.c: avoid potential kernel stack overflow
This can be triggered with root help only, but...
Register the ":text:E::txt::/root/cat.txt:' rule in binfmt_misc (by root) and
try launching the cat.txt file (by anyone) :) The result is - the endless
recursion in the load_misc_binary -> open_exec -> load_misc_binary chain and
stack overflow.
There's a similar problem with binfmt_script, and there's a sh_bang memner on
linux_binprm structure to handle this, but simply raising this in binfmt_misc
may break some setups when the interpreter of some misc binaries is a script.
So the proposal is to turn sh_bang into a bit, add a new one (the misc_bang)
and raise it in load_misc_binary. After this, even if we set up the misc ->
script -> misc loop for binfmts one of them will step on its own bang and
exit.
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | fs/binfmt_em86.c | 2 | ||||
| -rw-r--r-- | fs/binfmt_misc.c | 6 | ||||
| -rw-r--r-- | fs/binfmt_script.c | 2 | ||||
| -rw-r--r-- | include/linux/binfmts.h | 3 |
4 files changed, 10 insertions, 3 deletions
diff --git a/fs/binfmt_em86.c b/fs/binfmt_em86.c index f95ae9789c91..f9c88d0c8ced 100644 --- a/fs/binfmt_em86.c +++ b/fs/binfmt_em86.c @@ -43,7 +43,7 @@ static int load_em86(struct linux_binprm *bprm,struct pt_regs *regs) return -ENOEXEC; } - bprm->sh_bang++; /* Well, the bang-shell is implicit... */ + bprm->sh_bang = 1; /* Well, the bang-shell is implicit... */ allow_write_access(bprm->file); fput(bprm->file); bprm->file = NULL; diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c index dbf0ac0523de..7191306367c5 100644 --- a/fs/binfmt_misc.c +++ b/fs/binfmt_misc.c @@ -115,6 +115,12 @@ static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs) if (!enabled) goto _ret; + retval = -ENOEXEC; + if (bprm->misc_bang) + goto _ret; + + bprm->misc_bang = 1; + /* to keep locking time low, we copy the interpreter string */ read_lock(&entries_lock); fmt = check_file(bprm); diff --git a/fs/binfmt_script.c b/fs/binfmt_script.c index ab33939b12a7..9e3963f7ebf1 100644 --- a/fs/binfmt_script.c +++ b/fs/binfmt_script.c @@ -29,7 +29,7 @@ static int load_script(struct linux_binprm *bprm,struct pt_regs *regs) * Sorta complicated, but hopefully it will work. -TYT */ - bprm->sh_bang++; + bprm->sh_bang = 1; allow_write_access(bprm->file); fput(bprm->file); bprm->file = NULL; diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index 1dd756731c95..b512e48f6d8e 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -34,7 +34,8 @@ struct linux_binprm{ #endif struct mm_struct *mm; unsigned long p; /* current top of mem */ - int sh_bang; + unsigned int sh_bang:1, + misc_bang:1; struct file * file; int e_uid, e_gid; kernel_cap_t cap_inheritable, cap_permitted; |