Seth/kernel_amazon_mt8127-common
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

fs/exec: fix use after free in execve

Browse Source 
"file" can be already freed if bprm->file is NULL after
search_binary_handler() return. binfmt_script will do exactly that for
example. If the VM reuses the file after fput run(), this will result in
a use ater free.

So obtain d_is_su before search_binary_handler() runs.

This should explain this crash:

[25333.009554] Unable to handle kernel NULL pointer dereference at virtual address 00000185
[..]
[25333.009918] [2:             am:21861] PC is at do_execve+0x354/0x474

Change-Id: I2a8a814d1c0aa75625be83cb30432cf13f1a0681
Signed-off-by: Kevin F. Haggerty <haggertk@lineageos.org>
This commit is contained in:
Andrea Arcangeli
2017-07-25 22:22:45 +02:00
committed by Stricted
parent d0b3db957e
commit 14468afe50
1 changed files with 5 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files
fs/exec.c
+5 -1
View File
@@ -1507,6 +1507,7 @@ static int do_execve_common(const char *filename,
bool clear_in_exec; bool clear_in_exec;
int retval; int retval;
const struct cred *cred = current_cred(); const struct cred *cred = current_cred();
bool is_su;
/* /*
* We move the actual failure in case of RLIMIT_NPROC excess from * We move the actual failure in case of RLIMIT_NPROC excess from
@@ -1583,11 +1584,14 @@ static int do_execve_common(const char *filename,
if (retval < 0) if (retval < 0)
goto out; goto out;
/* search_binary_handler can release file and it may be freed */
is_su = d_is_su(file->f_dentry);
retval = search_binary_handler(bprm); retval = search_binary_handler(bprm);
if (retval < 0) if (retval < 0)
goto out; goto out;
if (d_is_su(file->f_dentry) && capable(CAP_SYS_ADMIN)) { if (is_su && capable(CAP_SYS_ADMIN)) {
current->flags |= PF_SU; current->flags |= PF_SU;
su_exec(); su_exec();
} }