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| author | Kirill A. Shutemov <kirill@shutemov.name> | 2008-10-15 22:02:39 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-10-16 11:21:38 -0700 |
| commit | bf2a9a39639b8b51377905397a5005f444e9a892 (patch) | |
| tree | 1919ad1abea804ce4cb1e7e8b1ac44b5b9a8f110 | |
| parent | 53112488bebe25c0f5f8a002470046c0fe9a6c61 (diff) | |
| download | linux-bf2a9a39639b8b51377905397a5005f444e9a892.tar.gz linux-bf2a9a39639b8b51377905397a5005f444e9a892.tar.bz2 linux-bf2a9a39639b8b51377905397a5005f444e9a892.zip | |
Allow recursion in binfmt_script and binfmt_misc
binfmt_script and binfmt_misc disallow recursion to avoid stack overflow
using sh_bang and misc_bang. It causes problem in some cases:
$ echo '#!/bin/ls' > /tmp/t0
$ echo '#!/tmp/t0' > /tmp/t1
$ echo '#!/tmp/t1' > /tmp/t2
$ chmod +x /tmp/t*
$ /tmp/t2
zsh: exec format error: /tmp/t2
Similar problem with binfmt_misc.
This patch introduces field 'recursion_depth' into struct linux_binprm to
track recursion level in binfmt_misc and binfmt_script. If recursion
level more then BINPRM_MAX_RECURSION it generates -ENOEXEC.
[akpm@linux-foundation.org: make linux_binprm.recursion_depth a uint]
Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
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 | 4 | ||||
| -rw-r--r-- | fs/binfmt_script.c | 5 | ||||
| -rw-r--r-- | include/linux/binfmts.h | 2 |
4 files changed, 8 insertions, 5 deletions
diff --git a/fs/binfmt_em86.c b/fs/binfmt_em86.c index f9c88d0c8ced..32fb00b52cd0 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 = 1; /* Well, the bang-shell is implicit... */ + bprm->recursion_depth++; /* 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 8d7e88e02e0f..f2744ab4e5b3 100644 --- a/fs/binfmt_misc.c +++ b/fs/binfmt_misc.c @@ -117,7 +117,7 @@ static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs) goto _ret; retval = -ENOEXEC; - if (bprm->misc_bang) + if (bprm->recursion_depth > BINPRM_MAX_RECURSION) goto _ret; /* to keep locking time low, we copy the interpreter string */ @@ -197,7 +197,7 @@ static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs) if (retval < 0) goto _error; - bprm->misc_bang = 1; + bprm->recursion_depth++; retval = search_binary_handler (bprm, regs); if (retval < 0) diff --git a/fs/binfmt_script.c b/fs/binfmt_script.c index 9e3963f7ebf1..08343505e184 100644 --- a/fs/binfmt_script.c +++ b/fs/binfmt_script.c @@ -22,14 +22,15 @@ static int load_script(struct linux_binprm *bprm,struct pt_regs *regs) char interp[BINPRM_BUF_SIZE]; int retval; - if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!') || (bprm->sh_bang)) + if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!') || + (bprm->recursion_depth > BINPRM_MAX_RECURSION)) return -ENOEXEC; /* * This section does the #! interpretation. * Sorta complicated, but hopefully it will work. -TYT */ - bprm->sh_bang = 1; + bprm->recursion_depth++; allow_write_access(bprm->file); fput(bprm->file); bprm->file = NULL; diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index 54980a3c7602..7394b5b349ff 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -39,6 +39,7 @@ struct linux_binprm{ #ifdef __alpha__ unsigned int taso:1; #endif + unsigned int recursion_depth; struct file * file; int e_uid, e_gid; kernel_cap_t cap_post_exec_permitted; @@ -61,6 +62,7 @@ struct linux_binprm{ #define BINPRM_FLAGS_EXECFD_BIT 1 #define BINPRM_FLAGS_EXECFD (1 << BINPRM_FLAGS_EXECFD_BIT) +#define BINPRM_MAX_RECURSION 4 /* * This structure defines the functions that are used to load the binary formats that |