| Message ID | 20201125075303.3963-1-ardb@kernel.org |
|---|---|
| State | Accepted |
| Commit | ff04f3b6f2e27f8ae28a498416af2a8dd5072b43 |
| Headers | show |
| Series | efivarfs: revert "fix memory leak in efivarfs_create()" | expand |
On Wed, 25 Nov 2020 at 09:05, Oleksandr Natalenko <oleksandr@natalenko.name> wrote: > > Hello. > > On 25.11.2020 08:53, Ard Biesheuvel wrote: > > The memory leak addressed by commit fe5186cf12e3 is a false positive: > > all allocations are recorded in a linked list, and freed when the > > filesystem is unmounted. This leads to double frees, and as reported > > by David, leads to crashes if SLUB is configured to self destruct when > > double frees occur. > > > > So drop the redundant kfree() again, and instead, mark the offending > > pointer variable so the allocation is ignored by kmemleak. > > > > Cc: Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@gmail.com> > > Should also have: > > Cc: <stable@vger.kernel.org> # v5.9 > No it should not. The fixes tag should be sufficient. > > Fixes: fe5186cf12e3 ("efivarfs: fix memory leak in efivarfs_create()") > > Reported-by: David Laight <David.Laight@aculab.com> > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > > --- > > fs/efivarfs/inode.c | 1 + > > fs/efivarfs/super.c | 1 - > > 2 files changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/fs/efivarfs/inode.c b/fs/efivarfs/inode.c > > index 96c0c86f3fff..38324427a2b3 100644 > > --- a/fs/efivarfs/inode.c > > +++ b/fs/efivarfs/inode.c > > @@ -103,6 +103,7 @@ static int efivarfs_create(struct inode *dir, > > struct dentry *dentry, > > var->var.VariableName[i] = '\0'; > > > > inode->i_private = var; > > + kmemleak_ignore(var); > > > > err = efivar_entry_add(var, &efivarfs_list); > > if (err) > > diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c > > index f943fd0b0699..15880a68faad 100644 > > --- a/fs/efivarfs/super.c > > +++ b/fs/efivarfs/super.c > > @@ -21,7 +21,6 @@ LIST_HEAD(efivarfs_list); > > static void efivarfs_evict_inode(struct inode *inode) > > { > > clear_inode(inode); > > - kfree(inode->i_private); > > } > > > > static const struct super_operations efivarfs_ops = { > > -- > Oleksandr Natalenko (post-factum)
On Wed, 25 Nov 2020 at 11:27, Oleksandr Natalenko <oleksandr@natalenko.name> wrote: > > On 25.11.2020 08:53, Ard Biesheuvel wrote: > > The memory leak addressed by commit fe5186cf12e3 is a false positive: > > all allocations are recorded in a linked list, and freed when the > > filesystem is unmounted. This leads to double frees, and as reported > > by David, leads to crashes if SLUB is configured to self destruct when > > double frees occur. > > > > So drop the redundant kfree() again, and instead, mark the offending > > pointer variable so the allocation is ignored by kmemleak. > > > > Cc: Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@gmail.com> > > Fixes: fe5186cf12e3 ("efivarfs: fix memory leak in efivarfs_create()") > > Reported-by: David Laight <David.Laight@aculab.com> > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > > --- > > fs/efivarfs/inode.c | 1 + > > fs/efivarfs/super.c | 1 - > > 2 files changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/fs/efivarfs/inode.c b/fs/efivarfs/inode.c > > index 96c0c86f3fff..38324427a2b3 100644 > > --- a/fs/efivarfs/inode.c > > +++ b/fs/efivarfs/inode.c > > @@ -103,6 +103,7 @@ static int efivarfs_create(struct inode *dir, > > struct dentry *dentry, > > var->var.VariableName[i] = '\0'; > > > > inode->i_private = var; > > + kmemleak_ignore(var); > > Do we need to do this as well: > > #include <linux/kmemleak.h> > > ? > > Because otherwise for 5.9 I get: > > [ 148s] fs/efivarfs/inode.c: In function 'efivarfs_create': > [ 148s] fs/efivarfs/inode.c:106:2: error: implicit declaration of > function 'kmemleak_ignore' [-Werror=implicit-function-declaration] > [ 148s] 106 | kmemleak_ignore(var); > [ 148s] | ^~~~~~~~~~~~~~~ > Ah yes, thanks for the report. I will add the include to the patch. > > > > err = efivar_entry_add(var, &efivarfs_list); > > if (err) > > diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c > > index f943fd0b0699..15880a68faad 100644 > > --- a/fs/efivarfs/super.c > > +++ b/fs/efivarfs/super.c > > @@ -21,7 +21,6 @@ LIST_HEAD(efivarfs_list); > > static void efivarfs_evict_inode(struct inode *inode) > > { > > clear_inode(inode); > > - kfree(inode->i_private); > > } > > > > static const struct super_operations efivarfs_ops = { > > -- > Oleksandr Natalenko (post-factum)
On 25/11/2020 10:28, Ard Biesheuvel wrote: > On Wed, 25 Nov 2020 at 11:27, Oleksandr Natalenko > <oleksandr@natalenko.name> wrote: >> >> On 25.11.2020 08:53, Ard Biesheuvel wrote: --snip-- >> >> Do we need to do this as well: >> >> #include <linux/kmemleak.h> >> >> ? >> >> Because otherwise for 5.9 I get: >> >> [ 148s] fs/efivarfs/inode.c: In function 'efivarfs_create': >> [ 148s] fs/efivarfs/inode.c:106:2: error: implicit declaration of >> function 'kmemleak_ignore' [-Werror=implicit-function-declaration] >> [ 148s] 106 | kmemleak_ignore(var); >> [ 148s] | ^~~~~~~~~~~~~~~ >> > > Ah yes, thanks for the report. I will add the include to the patch. > > Is this necessary if CONFIG_DEBUG_KMEMLEAK is not enabled in the kernel config? e.g. should there be an #ifdef CONFIG_DEBUG_KMEMLEAK somewhere in there?
On Fri, 27 Nov 2020 at 17:56, Jonathon Fernyhough <jonathon@m2x.dev> wrote: > > On 25/11/2020 10:28, Ard Biesheuvel wrote: > > On Wed, 25 Nov 2020 at 11:27, Oleksandr Natalenko > > <oleksandr@natalenko.name> wrote: > >> > >> On 25.11.2020 08:53, Ard Biesheuvel wrote: > --snip-- > >> > >> Do we need to do this as well: > >> > >> #include <linux/kmemleak.h> > >> > >> ? > >> > >> Because otherwise for 5.9 I get: > >> > >> [ 148s] fs/efivarfs/inode.c: In function 'efivarfs_create': > >> [ 148s] fs/efivarfs/inode.c:106:2: error: implicit declaration of > >> function 'kmemleak_ignore' [-Werror=implicit-function-declaration] > >> [ 148s] 106 | kmemleak_ignore(var); > >> [ 148s] | ^~~~~~~~~~~~~~~ > >> > > > > Ah yes, thanks for the report. I will add the include to the patch. > > > > > > Is this necessary if CONFIG_DEBUG_KMEMLEAK is not enabled in the kernel > config? e.g. should there be an #ifdef CONFIG_DEBUG_KMEMLEAK somewhere > in there? > We typically define these helpers unconditionally, and sort out the differences in the header file. In this case, we have static inline void kmemleak_ignore(const void *ptr) { } in include/linux/kmemleak.h if CONFIG_DEBUG_KMEMLEAK is not set. This makes the calling code much cleaner.
Hi. On Fri, Nov 27, 2020 at 04:50:34PM +0000, Jonathon Fernyhough wrote: > On 25/11/2020 10:28, Ard Biesheuvel wrote: > > On Wed, 25 Nov 2020 at 11:27, Oleksandr Natalenko > > <oleksandr@natalenko.name> wrote: > >> > >> On 25.11.2020 08:53, Ard Biesheuvel wrote: > --snip-- > >> > >> Do we need to do this as well: > >> > >> #include <linux/kmemleak.h> > >> > >> ? > >> > >> Because otherwise for 5.9 I get: > >> > >> [ 148s] fs/efivarfs/inode.c: In function 'efivarfs_create': > >> [ 148s] fs/efivarfs/inode.c:106:2: error: implicit declaration of > >> function 'kmemleak_ignore' [-Werror=implicit-function-declaration] > >> [ 148s] 106 | kmemleak_ignore(var); > >> [ 148s] | ^~~~~~~~~~~~~~~ > >> > > > > Ah yes, thanks for the report. I will add the include to the patch. > > > > > > Is this necessary if CONFIG_DEBUG_KMEMLEAK is not enabled in the kernel > config? e.g. should there be an #ifdef CONFIG_DEBUG_KMEMLEAK somewhere > in there? kmemleak_ignore() is a noop if CONFIG_DEBUG_KMEMLEAK is not set. See include/linux/kmemleak.h. Thus no extra condition is needed here. -- Oleksandr Natalenko (post-factum)
diff --git a/fs/efivarfs/inode.c b/fs/efivarfs/inode.c index 96c0c86f3fff..38324427a2b3 100644 --- a/fs/efivarfs/inode.c +++ b/fs/efivarfs/inode.c @@ -103,6 +103,7 @@ static int efivarfs_create(struct inode *dir, struct dentry *dentry, var->var.VariableName[i] = '\0'; inode->i_private = var; + kmemleak_ignore(var); err = efivar_entry_add(var, &efivarfs_list); if (err) diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c index f943fd0b0699..15880a68faad 100644 --- a/fs/efivarfs/super.c +++ b/fs/efivarfs/super.c @@ -21,7 +21,6 @@ LIST_HEAD(efivarfs_list); static void efivarfs_evict_inode(struct inode *inode) { clear_inode(inode); - kfree(inode->i_private); } static const struct super_operations efivarfs_ops = {
The memory leak addressed by commit fe5186cf12e3 is a false positive: all allocations are recorded in a linked list, and freed when the filesystem is unmounted. This leads to double frees, and as reported by David, leads to crashes if SLUB is configured to self destruct when double frees occur. So drop the redundant kfree() again, and instead, mark the offending pointer variable so the allocation is ignored by kmemleak. Cc: Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@gmail.com> Fixes: fe5186cf12e3 ("efivarfs: fix memory leak in efivarfs_create()") Reported-by: David Laight <David.Laight@aculab.com> Signed-off-by: Ard Biesheuvel <ardb@kernel.org> --- fs/efivarfs/inode.c | 1 + fs/efivarfs/super.c | 1 - 2 files changed, 1 insertion(+), 1 deletion(-)