Re: [PATCH] module: Fix use-after-free bug in read_file_mod_stats()
From: Harshit Mogalapalli <hidden>
Date: 2023-05-17 06:34:17
Also in:
kernel-janitors, lkml
Hi, On 28/04/23 11:29 am, Harshit Mogalapalli wrote:
Smatch warns: kernel/module/stats.c:394 read_file_mod_stats() warn: passing freed memory 'buf' We are passing 'buf' to simple_read_from_buffer() after freeing it. Fix this by changing the order of 'simple_read_from_buffer' and 'kfree'.
Friendly reminder to review this patch. Thanks, Harshit
quoted hunk ↗ jump to hunk
Fixes: df3e764d8e5c ("module: add debug stats to help identify memory pressure") Signed-off-by: Harshit Mogalapalli <redacted> --- Found with statis analysis, only compile tested. --- kernel/module/stats.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)diff --git a/kernel/module/stats.c b/kernel/module/stats.c index ad7b6ada29f2..6ab2c94d6bc3 100644 --- a/kernel/module/stats.c +++ b/kernel/module/stats.c@@ -276,6 +276,7 @@ static ssize_t read_file_mod_stats(struct file *file, char __user *user_buf, struct mod_fail_load *mod_fail; unsigned int len, size, count_failed = 0; char *buf; + int ret; u32 live_mod_count, fkreads, fdecompress, fbecoming, floads; unsigned long total_size, text_size, ikread_bytes, ibecoming_bytes, idecompress_bytes, imod_bytes, total_virtual_lost;@@ -390,8 +391,9 @@ static ssize_t read_file_mod_stats(struct file *file, char __user *user_buf, out_unlock: mutex_unlock(&module_mutex); out: + ret = simple_read_from_buffer(user_buf, count, ppos, buf, len); kfree(buf); - return simple_read_from_buffer(user_buf, count, ppos, buf, len); + return ret; } #undef MAX_PREAMBLE #undef MAX_FAILED_MOD_PRINT