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