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BUG/MEDIUM: vars: make functions vars_get_by_{name,desc} thread-safe

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This patch adds a lock to functions vars_get_by_name() and
vars_get_by_desc() to protect accesses to the list of variables.

After the variable is fetched, a sample data is duplicated by using
smp_dup() because the variable may be modified by another thread.

This should be backported to all versions supporting vars along with
"BUG/MINOR: sample: secure convs that accept base64 string and var name
as args" which this patch depends on.
This commit is contained in:
Dragan Dosen 2021-02-22 17:20:01 +01:00 committed by Willy Tarreau
parent 9e8db138c9
commit 14518f2305
1 changed files with 29 additions and 10 deletions
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39
src/vars.c
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@ -585,9 +585,13 @@ int vars_unset_by_name_ifexist(const char *name, size_t len, struct sample *smp)
}
/* this function fills a sample with the
* variable content. Returns 1 if the sample
* is filled, otherwise it returns 0.
/* This function fills a sample with the variable content.
*
* Keep in mind that a sample content is duplicated by using smp_dup()
* and it therefore uses a pre-allocated trash chunk as returned by
* get_trash_chunk().
*
* Returns 1 if the sample is filled, otherwise it returns 0.
*/
int vars_get_by_name(const char *name, size_t len, struct sample *smp)
{
@ -606,19 +610,29 @@ int vars_get_by_name(const char *name, size_t len, struct sample *smp)
return 0;
/* Get the variable entry. */
HA_RWLOCK_RDLOCK(VARS_LOCK, &vars->rwlock);
var = var_get(vars, name);
if (!var)
if (!var) {
HA_RWLOCK_RDUNLOCK(VARS_LOCK, &vars->rwlock);
return 0;
}
/* Copy sample. */
smp->data = var->data;
smp->flags = SMP_F_CONST;
smp_dup(smp);
HA_RWLOCK_RDUNLOCK(VARS_LOCK, &vars->rwlock);
return 1;
}
/* this function fills a sample with the
* content of the variable described by <var_desc>. Returns 1
* if the sample is filled, otherwise it returns 0.
/* This function fills a sample with the content of the variable described
* by <var_desc>.
*
* Keep in mind that a sample content is duplicated by using smp_dup()
* and it therefore uses a pre-allocated trash chunk as returned by
* get_trash_chunk().
*
* Returns 1 if the sample is filled, otherwise it returns 0.
*/
int vars_get_by_desc(const struct var_desc *var_desc, struct sample *smp)
{
@ -633,13 +647,18 @@ int vars_get_by_desc(const struct var_desc *var_desc, struct sample *smp)
return 0;
/* Get the variable entry. */
HA_RWLOCK_RDLOCK(VARS_LOCK, &vars->rwlock);
var = var_get(vars, var_desc->name);
if (!var)
if (!var) {
HA_RWLOCK_RDUNLOCK(VARS_LOCK, &vars->rwlock);
return 0;
}
/* Copy sample. */
smp->data = var->data;
smp->flags = SMP_F_CONST;
smp_dup(smp);
HA_RWLOCK_RDUNLOCK(VARS_LOCK, &vars->rwlock);
return 1;
}