| Message ID | 20191217194528.16461-1-tli@digitalocean.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drivers/misc: have the callers of set_memory_*() check the return value | expand |
On Tue, Dec 17, 2019 at 01:45:28PM -0600, Tianlin Li wrote: > Right now several architectures allow their set_memory_*() family of > functions to fail, but callers may not be checking the return values. > If set_memory_*() returns with an error, call-site assumptions may be > infact wrong to assume that it would either succeed or not succeed at > all. Ideally, the failure of set_memory_*() should be passed up the > call stack, and callers should examine the failure and deal with it. > > Need to fix the callers and add the __must_check attribute. They also > may not provide any level of atomicity, in the sense that the memory > protections may be left incomplete on failure. This issue likely has a > few steps on effects architectures: > 1)Have all callers of set_memory_*() helpers check the return value. > 2)Add __must_check to all set_memory_*() helpers so that new uses do > not ignore the return value. > 3)Add atomicity to the calls so that the memory protections aren't left > in a partial state. > > This series is part of step 1. Make sram driver check the return value of > set_memory_*(). > > Signed-off-by: Tianlin Li <tli@digitalocean.com> Reviewed-by: Kees Cook <keescook@chromium.org> -Kees > --- > drivers/misc/sram-exec.c | 21 +++++++++++++++++---- > 1 file changed, 17 insertions(+), 4 deletions(-) > > diff --git a/drivers/misc/sram-exec.c b/drivers/misc/sram-exec.c > index d054e2842a5f..cb57ac6ab4c3 100644 > --- a/drivers/misc/sram-exec.c > +++ b/drivers/misc/sram-exec.c > @@ -85,6 +85,7 @@ void *sram_exec_copy(struct gen_pool *pool, void *dst, void *src, > unsigned long base; > int pages; > void *dst_cpy; > + int ret; > > mutex_lock(&exec_pool_list_mutex); > list_for_each_entry(p, &exec_pool_list, list) { > @@ -104,16 +105,28 @@ void *sram_exec_copy(struct gen_pool *pool, void *dst, void *src, > > mutex_lock(&part->lock); > > - set_memory_nx((unsigned long)base, pages); > - set_memory_rw((unsigned long)base, pages); > + ret = set_memory_nx((unsigned long)base, pages); > + if (ret) > + goto error_out; > + ret = set_memory_rw((unsigned long)base, pages); > + if (ret) > + goto error_out; > > dst_cpy = fncpy(dst, src, size); > > - set_memory_ro((unsigned long)base, pages); > - set_memory_x((unsigned long)base, pages); > + ret = set_memory_ro((unsigned long)base, pages); > + if (ret) > + goto error_out; > + ret = set_memory_x((unsigned long)base, pages); > + if (ret) > + goto error_out; > > mutex_unlock(&part->lock); > > return dst_cpy; > + > +error_out: > + mutex_unlock(&part->lock); > + return NULL; > } > EXPORT_SYMBOL_GPL(sram_exec_copy); > -- > 2.17.1 >
diff --git a/drivers/misc/sram-exec.c b/drivers/misc/sram-exec.c index d054e2842a5f..cb57ac6ab4c3 100644 --- a/drivers/misc/sram-exec.c +++ b/drivers/misc/sram-exec.c @@ -85,6 +85,7 @@ void *sram_exec_copy(struct gen_pool *pool, void *dst, void *src, unsigned long base; int pages; void *dst_cpy; + int ret; mutex_lock(&exec_pool_list_mutex); list_for_each_entry(p, &exec_pool_list, list) { @@ -104,16 +105,28 @@ void *sram_exec_copy(struct gen_pool *pool, void *dst, void *src, mutex_lock(&part->lock); - set_memory_nx((unsigned long)base, pages); - set_memory_rw((unsigned long)base, pages); + ret = set_memory_nx((unsigned long)base, pages); + if (ret) + goto error_out; + ret = set_memory_rw((unsigned long)base, pages); + if (ret) + goto error_out; dst_cpy = fncpy(dst, src, size); - set_memory_ro((unsigned long)base, pages); - set_memory_x((unsigned long)base, pages); + ret = set_memory_ro((unsigned long)base, pages); + if (ret) + goto error_out; + ret = set_memory_x((unsigned long)base, pages); + if (ret) + goto error_out; mutex_unlock(&part->lock); return dst_cpy; + +error_out: + mutex_unlock(&part->lock); + return NULL; } EXPORT_SYMBOL_GPL(sram_exec_copy);
Right now several architectures allow their set_memory_*() family of functions to fail, but callers may not be checking the return values. If set_memory_*() returns with an error, call-site assumptions may be infact wrong to assume that it would either succeed or not succeed at all. Ideally, the failure of set_memory_*() should be passed up the call stack, and callers should examine the failure and deal with it. Need to fix the callers and add the __must_check attribute. They also may not provide any level of atomicity, in the sense that the memory protections may be left incomplete on failure. This issue likely has a few steps on effects architectures: 1)Have all callers of set_memory_*() helpers check the return value. 2)Add __must_check to all set_memory_*() helpers so that new uses do not ignore the return value. 3)Add atomicity to the calls so that the memory protections aren't left in a partial state. This series is part of step 1. Make sram driver check the return value of set_memory_*(). Signed-off-by: Tianlin Li <tli@digitalocean.com> --- drivers/misc/sram-exec.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-)