Re: [PATCH] efi_loader: fix string table reallocations

["Vincent Stehlé" <vincent.stehle@arm.com>]

On Thu, Sep 17, 2026 at 06:23:11PM +0200, Heinrich Schuchardt wrote:
> Am 17. September 2026 11:45:31 MESZ schrieb "Vincent Stehlé" <vincent.stehle@arm.com>:
> >The new_string() and set_string() HII string protocol functions keep
> >using old pointers after calling realloc(), which may have moved.
> >
> >The set_string() function also assumes that reallocation only grew the
> >array by one element when computing the start of the memory to clear,
> >and forgets to update nstrings to the new table size after reallocation.
> >
> >Repair and factorize the reallocation code in a new grow_string_table()
> >function to fix those issues.
> 
> 
> Should we add a test in U-Boot and possibly in SCT?

Hi Heinrich,

Thanks for having a look.

I think the existing "HII database protocols" self-test is sufficient, thanks to
the change.

With this test, before the patch, the code coverage is fairly good in
new_string() but is poor in set_string().

After the patch, the code coverage of grow_string_table() is fairly good as
expected, and the poor code coverage of set_string() is "gone".

Best regards,
Vincent.

> 
> Best regards
> 
> Heinrich
> 
> >
> >Fixes: c9bfb22296b0 ("efi_loader: Initial HII database protocols")
> >Signed-off-by: Vincent Stehlé <vincent.stehle@arm.com>
> >Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
> >Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
> >Cc: Tom Rini <trini@konsulko.com>
> >---
> >This can be tested on the sandbox with the following command:
> >
> >  ./u-boot -T -c 'setenv efi_selftest HII database protocols; bootefi selftest'
> >
> >While the unit test does cause reallocation with new_string(), it does not
> >with set_string().
> >
> >Further testing can be done by forcing stbl->strings = NULL, just after
> >calling realloc(stbl->strings, ...).
> >---
> > lib/efi_loader/efi_hii.c | 64 +++++++++++++++++++++++++++---------------------
> > 1 file changed, 36 insertions(+), 28 deletions(-)
> >
> >diff --git a/lib/efi_loader/efi_hii.c b/lib/efi_loader/efi_hii.c
> >index 7bf51ad43d1..90dff91e5d4 100644
> >--- a/lib/efi_loader/efi_hii.c
> >+++ b/lib/efi_loader/efi_hii.c
> >@@ -822,6 +822,37 @@ static bool language_match(char *language, char *languages)
> > 	return false;
> > }
> > 
> >+/**
> >+ * grow_string_table() - Grow a string table if necessary.
> >+ * @stbl: String table to grow.
> >+ * @n:    Minimum table size desired.
> >+ *
> >+ * Make sure a string table can contain at least n elements.
> >+ * If the table is too small, reallocate the memory and clear the new elements.
> >+ *
> >+ * Return: false in case of reallocation error, true otherwise.
> >+ * In case of error, the original string table is left untouched.
> >+ * In case of success, stbl->strings and stbl->nstrings may have been updated.
> >+ */
> >+static bool grow_string_table(struct efi_string_table *stbl, u32 n)
> >+{
> >+	void *buf;
> >+	u32 old_n = stbl->nstrings;
> >+
> >+	if (old_n >= n)
> >+		return true;
> >+
> >+	buf = realloc(stbl->strings, sizeof(stbl->strings[0]) * n);
> >+	if (!buf)
> >+		return false;
> >+
> >+	stbl->strings = buf;
> >+	stbl->nstrings = n;
> >+	memset(&stbl->strings[old_n], 0, sizeof(stbl->strings[0]) * (n - old_n));
> >+
> >+	return true;
> >+}
> >+
> > static efi_status_t EFIAPI
> > new_string(const struct efi_hii_string_protocol *this,
> > 	   efi_hii_handle_t package_list,
> >@@ -847,23 +878,12 @@ new_string(const struct efi_hii_string_protocol *this,
> > 	list_for_each_entry(stbl, &hii->string_tables, link) {
> > 		if (language_match((char *)language, stbl->language)) {
> > 			efi_string_id_t new_id;
> >-			void *buf;
> > 			efi_string_t str;
> > 
> > 			new_id = ++hii->max_string_id;
> >-			if (stbl->nstrings < new_id) {
> >-				buf = realloc(stbl->strings,
> >-					      sizeof(stbl->strings[0])
> >-						* new_id);
> >-				if (!buf)
> >-					return EFI_EXIT(EFI_OUT_OF_RESOURCES);
> >-
> >-				memset(&stbl->strings[stbl->nstrings], 0,
> >-				       (new_id - stbl->nstrings)
> >-					 * sizeof(stbl->strings[0]));
> >-				stbl->strings = buf;
> >-				stbl->nstrings = new_id;
> >-			}
> >+
> >+			if (!grow_string_table(stbl, new_id))
> >+				return EFI_EXIT(EFI_OUT_OF_RESOURCES);
> > 
> > 			str = u16_strdup(string);
> > 			if (!str)
> >@@ -957,20 +977,8 @@ set_string(const struct efi_hii_string_protocol *this,
> > 			if (hii->max_string_id < string_id)
> > 				return EFI_EXIT(EFI_NOT_FOUND);
> > 
> >-			if (stbl->nstrings < string_id) {
> >-				void *buf;
> >-
> >-				buf = realloc(stbl->strings,
> >-					      string_id
> >-						* sizeof(stbl->strings[0]));
> >-				if (!buf)
> >-					return EFI_EXIT(EFI_OUT_OF_RESOURCES);
> >-
> >-				memset(&stbl->strings[string_id - 1], 0,
> >-				       (string_id - stbl->nstrings)
> >-					 * sizeof(stbl->strings[0]));
> >-				stbl->strings = buf;
> >-			}
> >+			if (!grow_string_table(stbl, string_id))
> >+				return EFI_EXIT(EFI_OUT_OF_RESOURCES);
> > 
> > 			str = u16_strdup(string);
> > 			if (!str)
> >
> >---
> >base-commit: 2c7eaee7b3422ce7c84e892abfe16e1afce42e83
> >change-id: 20260916-ptr-670be74dcbd3
> >
> >Best regards,
> >--  
> >Vincent.
> >
> 

-- 
Vincent.