The implementation of syscall_get_nr on mips used to ignore the task
argument and return the syscall number of the calling thread instead of
the target thread.
The bug was exposed to user space by commit 201766a20e30f ("ptrace: add
PTRACE_GET_SYSCALL_INFO request") and detected by strace test suite.
Link: https://github.com/strace/strace/issues/235
Fixes: c2d9f1775731 ("MIPS: Fix syscall_get_nr for the syscall exit tracing.")
Cc: <stable(a)vger.kernel.org> # v3.19+
Co-developed-by: Dmitry V. Levin <ldv(a)strace.io>
Signed-off-by: Dmitry V. Levin <ldv(a)strace.io>
Signed-off-by: Elvira Khabirova <lineprinter0(a)gmail.com>
---
arch/mips/include/asm/syscall.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/mips/include/asm/syscall.h b/arch/mips/include/asm/syscall.h
index 25fa651c937d..ebdf4d910af2 100644
--- a/arch/mips/include/asm/syscall.h
+++ b/arch/mips/include/asm/syscall.h
@@ -38,7 +38,7 @@ static inline bool mips_syscall_is_indirect(struct task_struct *task,
static inline long syscall_get_nr(struct task_struct *task,
struct pt_regs *regs)
{
- return current_thread_info()->syscall;
+ return task_thread_info(task)->syscall;
}
static inline void mips_syscall_update_nr(struct task_struct *task,
--
With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG),
indirect call targets are validated against the expected function
pointer prototype to make sure the call target is valid to help mitigate
ROP attacks. If they are not identical, there is a failure at run time,
which manifests as either a kernel panic or thread getting killed.
ext4_feat_ktype was setting the "release" handler to "kfree", which
doesn't have a matching function prototype. Add a simple wrapper
with the correct prototype.
This was found as a result of Clang's new -Wcast-function-type-strict
flag, which is more sensitive than the simpler -Wcast-function-type,
which only checks for type width mismatches.
Note that this code is only reached when ext4 is a loadable module and
it is being unloaded:
CFI failure at kobject_put+0xbb/0x1b0 (target: kfree+0x0/0x180; expected type: 0x7c4aa698)
...
RIP: 0010:kobject_put+0xbb/0x1b0
...
Call Trace:
<TASK>
ext4_exit_sysfs+0x14/0x60 [ext4]
cleanup_module+0x67/0xedb [ext4]
Fixes: b99fee58a20a ("ext4: create ext4_feat kobject dynamically")
Cc: Theodore Ts'o <tytso(a)mit.edu>
Cc: Eric Biggers <ebiggers(a)kernel.org>
Cc: stable(a)vger.kernel.org
Build-tested-by: Gustavo A. R. Silva <gustavoars(a)kernel.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars(a)kernel.org>
Reviewed-by: Nathan Chancellor <nathan(a)kernel.org>
Link: https://lore.kernel.org/r/20230103234616.never.915-kees@kernel.org
Signed-off-by: Kees Cook <keescook(a)chromium.org>
---
v2: rename callback, improve commit log (ebiggers)
v1: https://lore.kernel.org/lkml/20230103234616.never.915-kees@kernel.org
---
fs/ext4/sysfs.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c
index d233c24ea342..e2b8b3437c58 100644
--- a/fs/ext4/sysfs.c
+++ b/fs/ext4/sysfs.c
@@ -491,6 +491,11 @@ static void ext4_sb_release(struct kobject *kobj)
complete(&sbi->s_kobj_unregister);
}
+static void ext4_feat_release(struct kobject *kobj)
+{
+ kfree(kobj);
+}
+
static const struct sysfs_ops ext4_attr_ops = {
.show = ext4_attr_show,
.store = ext4_attr_store,
@@ -505,7 +510,7 @@ static struct kobj_type ext4_sb_ktype = {
static struct kobj_type ext4_feat_ktype = {
.default_groups = ext4_feat_groups,
.sysfs_ops = &ext4_attr_ops,
- .release = (void (*)(struct kobject *))kfree,
+ .release = ext4_feat_release,
};
void ext4_notify_error_sysfs(struct ext4_sb_info *sbi)
--
2.34.1