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SubjectRe: [PATCH] staging: lustre: mgc: fix potential use after free in error path


On Mon, 7 Aug 2017, Cihangir Akturk wrote:

> The config_log_add() function first calls config_log_put() with the
> variable 'cld' and then jumps to label 'out_cld', which will call
> the same function with the same 'cld' variable. However, at this
> point, 'cld' might have been already freed by the first invocation
> of config_log_put(). Even if we remove the invocation at that point,
> we will still get into trouble. This is because, in the error path,
> just below the label 'out_cld', we try to put 'params_cls' and
> 'sptlrpc_cld', which might also have been freed by config_log_put().
>
> The point is that, config_llog_data::cld_sptlrpc and
> config_llog_data::cld_params members are assigned at the beginning
> of this function.
>
> To avoid this, do not call config_log_put() inside the else block,
> immediately jump to 'out_cld' instead. Moreover, remove assignments
> to config_llog_data::cld_sptlrpc and config_llog_data::cld_params at
> the beginning, since we already assign them below in the function
> with 'cld_lock' held.
>
> As an additional benefit, code size gets smaller.
>
> before:
> text data bss dec hex filename
> 26188 2256 4208 32652 7f8c drivers/staging/lustre/lustre/mgc/mgc_request.o
>
> after:
> text data bss dec hex filename
> 26092 2256 4208 32556 7f2c drivers/staging/lustre/lustre/mgc/mgc_request.o
>
> Signed-off-by: Cihangir Akturk <cakturk@gmail.com>
> ---
> drivers/staging/lustre/lustre/mgc/mgc_request.c | 16 +++-------------
> 1 file changed, 3 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/staging/lustre/lustre/mgc/mgc_request.c b/drivers/staging/lustre/lustre/mgc/mgc_request.c
> index eee0b66..36c3049 100644
> --- a/drivers/staging/lustre/lustre/mgc/mgc_request.c
> +++ b/drivers/staging/lustre/lustre/mgc/mgc_request.c
> @@ -288,7 +288,7 @@ config_log_add(struct obd_device *obd, char *logname,
> struct config_llog_data *cld;
> struct config_llog_data *sptlrpc_cld;
> struct config_llog_data *params_cld;
> - bool locked = false;
> + struct config_llog_data *recover_cld = NULL;
> char seclogname[32];
> char *ptr;
> int rc;
> @@ -333,20 +333,14 @@ config_log_add(struct obd_device *obd, char *logname,
> goto out_params;
> }
>
> - cld->cld_sptlrpc = sptlrpc_cld;
> - cld->cld_params = params_cld;
> -
> LASSERT(lsi->lsi_lmd);
> if (!(lsi->lsi_lmd->lmd_flags & LMD_FLG_NOIR)) {
> - struct config_llog_data *recover_cld;
> -
> ptr = strrchr(seclogname, '-');
> if (ptr) {
> *ptr = 0;
> } else {
> CERROR("%s: sptlrpc log name not correct, %s: rc = %d\n",
> obd->obd_name, seclogname, -EINVAL);
> - config_log_put(cld);
> rc = -EINVAL;
> goto out_cld;
> }
> @@ -355,14 +349,10 @@ config_log_add(struct obd_device *obd, char *logname,
> rc = PTR_ERR(recover_cld);
> goto out_cld;
> }
> -
> - mutex_lock(&cld->cld_lock);
> - locked = true;
> - cld->cld_recover = recover_cld;
> }
>
> - if (!locked)
> - mutex_lock(&cld->cld_lock);
> + mutex_lock(&cld->cld_lock);
> + cld->cld_recover = recover_cld;
> cld->cld_params = params_cld;
> cld->cld_sptlrpc = sptlrpc_cld;
> mutex_unlock(&cld->cld_lock);
> --
> 2.7.4

Reviewed-by: James Simmons <jsimmons@infradead.org>

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